Climate Change & Greenhouse Gas Emissions: Causes, Sources, Effects, Solutions & Forecasts

Climate Change & Greenhouse Gas Emissions: Causes, Sources, Effects, Solutions & Forecasts

Climate change is one of the most talked about, if not the most talked about global issue.

When we talk about Climate Change, we also usually talk about global warming and greenhouse gases.

In this guide we outline what climate change is, the causes and sources, the effects, and what potential solutions might be on how to prevent it.

We also talk about how global warming and greenhouse gases tie into climate change as a whole.


Summary – What To Know About Climate Change

Climate change in a nutshell is the warming of the earth’s surface (via the sun’s solar radiation, and eventually infrared radiation) – with the warming process being amplified by greenhouse gases such as carbon dioxide (the main gas), but also methane, nitrous oxide and other gases.

From the evidence gathered, climate modelling done, and scientific formulas used – there is a consensus that humans are most likely the primary cause for the warming we are seeing today. Activities such as electricity production (that burns fossil fuels like coal), and vehicles (that burn petroleum) emit huge amounts of GHGs through burning of fossil fuels.

This warming period is usually expressed as the warming that has taken place since around 1950/60.

Temperatures have risen (up to 2019) around 0.8 to 0.9 degrees celcius compared to pre industrial levels, when carbon dioxide levels started increasing rapidly.

This rapid increase in carbon dioxide level (parts per million in the air) coincides with humans’ increased combustion of fossil fuels since the start of the industrial revolution.

What scientists do admit is that there are things they do know about climate change, things they think they might know, and things they are uncertain about that they can only make educated forecasts about with the information available.

They also admit that climate change feedback processes can be complex – leading to warming in some areas, and cooling in others (each area in the world has it’s own local or micro climate).

There’s also variables in the form of what we as humans will do in the future. What we do to mitigate emissions, adapt to changes, and reduce emissions will all impact how climate predictions can be made into the future.

As mentioned above, when it comes to climate change, a good way to look at it might be – what we are fairly certain we know, what we think we might know, and what we might be uncertain about.


What Is Climate Change?

  • Climate change is a change in the pattern of weather, and related changes in oceans, land surfaces and ice sheets, occurring over time scales of decades or longer



What Is Global Warming?

Global warming (i.e. an increase in the earth’s surface temperature) is just one factor in the overall climate change issue.

So, climate change is the all encompassing issue, whereas global warming is a ‘sub factor’ or ‘side effect’ in the overall issue.


What Is The Main Climate Change Problem?

It’s a very wide ranging problem with many factors and sub issues, causes, effects etc. to consider.

These factors and specific issues also differ country by country (and even state by state).

But, the core of the problem is the rise in the earth’s average surface temperature since the industrial revolution and particularly since the late 19th century, which has been largely driven by increased carbon dioxide and other human caused emissions in the atmosphere (carbon dioxide levels have sharply increased to unseen levels from 1950 to the current day).

A big cause for this is the burning of fossil fuels for electricity and heat production, transportation, industry (factories and production of goods and raw materials), and agriculture and clearing of land.


The planet’s average surface temperature has risen about 1.62 degrees Fahrenheit (0.9 degrees Celsius) since the late 19th century.

Most of the warming occurred in the past 35 years, with the five warmest years on record taking place since 2010. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year — from January through September, with the exception of June — were the warmest on record for those respective months.

Temperature is the one that gets all the attention, but there’s also other issues like:

  • Warming oceans
  • Shrinking ice sheets
  • Glacial retreat
  • Decreased snow cover
  • Sea level rise
  • Declining Arctic sea ice
  • Extreme/severe natural events
  • Ocean acidification
  • + more



What Are Greenhouse Gases?

Greenhouse gases are gases emitted from human and natural sources on earth, that rise up and sit in the earth’s atmosphere like a blanket.

This blanket of greenhouse gases lets through solar radiation from the sun (light). It also absorbs and re-emits infrared radiation (heat) from and back to the earth’s surface.

They get the name greenhouse gas because they have a similar effect that greenhouse glass has whereby the glass traps some IR radiation heat inside the greenhouse.

Greenhouse gases can be divided into two main types:

  • Greenhouse gases being emitted directly by human activities – Carbon dioxide (CO2) is the main one. Then methane (CH4), and nitrous oxide (N2O). Then others include ozone (O3), and synthetic gases (the ‘F’ gases), such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs)
  • Other greenhouse gases – Water vapour is also a major greenhouse gas, but its concentration in the atmosphere is not influenced directly by human activities (it is influenced indirectly though by the production of carbon dioxide).
  • The most important greenhouse gases are water vapour and carbon dioxide (CO2). Both are present at very small concentrations in the atmosphere.
  • The two most abundant gases in the atmosphere are nitrogen (comprising 78 per cent of the dry atmosphere) and oxygen (21 per cent), but they have almost no greenhouse effects.
  • Water vapour varies considerably in space and time because it has a short ‘lifetime’ in the atmosphere. Because of this variation, it is difficult to measure globally averaged water vapour concentration.
  • Carbon dioxide has a much longer lifetime and is well mixed throughout the atmosphere. The current concentration is about 0.04 per cent.



  • Today, human activities are directly increasing atmospheric concentrations of CO2, methane and nitrous oxide, plus some chemically manufactured greenhouse gases such as halocarbons.
  • These human generated gases enhance the natural greenhouse effect and further warm the surface.
  • In addition to the direct effect, the warming that results from increased concentrations of long-lived greenhouse gases can be amplified by other processes.
  • A key example is water vapour amplification. Human activities are also increasing aerosols in the atmosphere, which reflect some incoming sunlight. This human-induced change offsets some of the warming from greenhouse gases.



What Is The Greenhouse Gas Effect?

There are two main types of greenhouse gas effects:

  • The natural green house gas effect which happens via the natural carbon cycle
  • The enhanced greenhouse gas effect which happens via human activities that add carbon dioxide on top of the natural emission of carbon dioxide

The thing is – we need the natural carbon cycle and natural greenhouse gas effect to make earth habitable. Without it, the earth would be -18ºC (minus 18 degrees) – and the earth would be uninhabitable.

The problem is the enhanced/human induced greenhouse releases carbon into the atmosphere faster than it can be removed by other parts of the carbon cycle.

This is called the ‘greenhouse effect’, and the gases that cause it by interacting with infrared radiation are called greenhouse gases. The most important are water vapour (which humans can’t directly control), carbon dioxide (CO2) and methane.

Since the Industrial Revolution, energy-driven consumption of fossil fuels has led to a rapid increase in CO2 emissions, disrupting the global carbon cycle and leading to a planetary warming impact.



How Does The Greenhouse Effect Actually Work?

What happens in the greenhouse effect it:

  • Solar radiation (light) comes from the sun and is emitted onto the earth’s surface (the sun’s energy intensity and the distance of the sun from earth affect how much solar radiation we get)
  • This solar radiation hits the earth’s surface, is converted to IR radiataion (heat) and warms the earth
  • Some IR radiation is emitted back to space, and some of it does escape into space
  • Some IR radiation gets absorbed by greenhouse gases in the atmosphere and re-emitted back onto the earth’s surface and troposphere – causing more heating than normal
  • Greenhouse gases, particularly carbon, gather in the atmosphere at a higher rate due to human activity like burning fossil fuels than they would during the natural carbon cycle

You can see how this works visually here:

the greenhouse effect

Credit: Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal

Page Link:


  • The Sun serves as the primary energy source for Earth’s climate.
  • Some of the incoming sunlight is reflected directly back into space, especially by bright surfaces such as ice and clouds, and the rest is absorbed by the surface and the atmosphere.
  • Much of this absorbed solar energy is re-emitted as heat (longwave or infrared radiation).
  • The atmosphere in turn absorbs and re-radiates heat, some of which escapes to space. Any disturbance to this balance of incoming and outgoing energy will affect the climate. For example, small changes in the output of energy from the Sun will affect this balance directly.
  • If all heat energy emitted from the surface passed through the atmosphere directly into space, Earth’s average surface temperature would be tens of degrees colder than today. Greenhouse gases in the atmosphere, including water vapour, carbon dioxide, methane, and nitrous oxide, act to make the surface much warmer than this, because they absorb and emit heat energy in all directions (including downwards), keeping Earth’s surface and lower atmosphere warm.
  • Without this greenhouse effect, life as we know it could not have evolved on our planet.
  • Adding more greenhouse gases to the atmosphere makes it even more effective at preventing heat from escaping into space.
  • When the energy leaving is less than the energy entering, Earth warms until a new balance is established.



What Is The Natural Carbon Cycle, And The Natural Greenhouse Gas Effect?

The natural cycle of carbon emission and absorption into and out of the atmosphere by living things and the natural environment.

All living organisms contain carbon, as do gases (such as carbon dioxide) and minerals (such as diamond, peat and coal). The movement of carbon between large natural reservoirs in rocks, the ocean, the atmosphere, plants, soil and fossil fuels is known as the carbon cycle.

The carbon cycle includes the movement of carbon dioxide:

  • into and out of our atmosphere
  • between the atmosphere, plants and other living organisms through photosynthesis, respiration and decay
  • between the atmosphere and the top of the oceans.

On longer time scales, chemical weathering and limestone and fossil fuel formation decrease atmospheric carbon dioxide levels, whereas volcanoes return carbon to the atmosphere. This is the dominant mechanism of control of carbon dioxide on timescales of millions of years.

Because the carbon cycle is essentially a closed system, any decrease in one reservoir of carbon leads to an increase in others.

For at least the last several hundred thousand years, up until the Industrial Revolution, natural sources of carbon dioxide were in approximate balance with natural ‘sinks’, producing relatively stable levels of atmospheric carbon dioxide.

‘Sinks’ are oceans, plants and soils, which absorb more carbon dioxide than they emit (in contrast, carbon sources emit more than they absorb).



What Is The Human/Enhanced Greenhouse Gas Effect?

Greenhouse gases (mainly carbon dioxide) emitted into the atmosphere mainly by human activity.

Refer to the ’causes’ section below for the sources of these carbon dioxide emissions.

The total carbon cycle is the natural carbon cycle and human carbon cycle together. That can be seen here:

total carbon cycle

Credit: Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal



Why Is Carbon Dioxide Considered The Main Greenhouse Gas?

There’s two reasons for this:

  • CO2 is responsible for more of an increase in the amount of energy (and therefore heat) reaching Earth’s surface than the other greenhouse gases. Other gases have more potent heat-trapping ability molecule per molecule than CO2 (e.g. methane), but are simply far less abundant in the atmosphere.
  • CO2 remains in the atmosphere longer than the other major heat-trapping gases


Explained in deeper detail…

  • Greenhouse gases are climate drivers
  • By measuring the abundance of heat-trapping gases in ice cores, the atmosphere, and other climate drivers along with models, the IPCC calculated the “radiative forcing” (RF) of each climate driver—in other words, the net increase (or decrease) in the amount of energy reaching Earth’s surface attributable to that climate driver.
  • Positive RF values represent average surface warming and negative values represent average surface cooling. In total, CO2 has the highest positive RF (see Figure 1) of all the human-influenced climate drivers compared by the IPCC.
  • Other gases have more potent heat-trapping ability molecule per molecule than CO2 (e.g. methane), but are simply far less abundant in the atmosphere.
  • CO2 remains in the atmosphere longer than the other major heat-trapping gases emitted as a result of human activities. It takes about a decade for methane (CH4) emissions to leave the atmosphere (it converts into CO2) and about a century for nitrous oxide (N2O).
  • After a pulse of CO2 is emitted into the atmosphere, 40% will remain in the atmosphere for 100 years and 20% will reside for 1000 years, while the final 10% will take 10,000 years to turn over. This literally means that the heat-trapping emissions we release today from our cars and power plants are setting the climate our children and grandchildren will inherit.
  • Water vapor is the most abundant heat-trapping gas, but rarely discussed when considering human-induced climate change. The principal reason is that water vapor has a short cycle in the atmosphere (10 days on average) before it is incorporated into weather events and falls to Earth, so it cannot build up in the atmosphere in the same way as carbon dioxide does.
  • However, a vicious cycle exists with water vapor, in which as more CO2 is emitted into the atmosphere and the Earth’s temperature rises, more water evaporates into the Earth’s atmosphere, which increases the temperature of the planet. The higher temperature atmosphere can then hold more water vapor than before.



Explained in another way…

  • Carbon dioxide is not the only greenhouse gas of concern for global warming and climatic change. There are a range of greenhouse gases, which include methane, nitrous oxide, and a range of smaller concentration trace gases such as the so-called group of ‘F-gases’.
  • Greenhouse gases vary in their relative contributions to global warming; i.e. one tonne of methane does not have the same impact on warming as one tonne of carbon dioxide. These differences can be defined using a metric called ‘Global Warming Potential’ (GWP). GWP can be defined on a range of time-periods, however the most commonly used (and that adopted by the IPCC) is the 100-year timescale (GWP100).
  • You can look at the GWP100 value of key greenhouse gases relative to carbon dioxide. The GWP100metric measures the relative warming impact one molecule or unit mass of a greenhouse gas relative to carbon dioxide over a 100-year timescale. For example, one tonne of methane would have 28 times the warming impact of tonne of carbon dioxide over a 100-year period. GWP100 values are used to combine greenhouse gases into a single metric of emissions called carbon dioxide equivalents (CO2e). CO2e is derived by multiplying the mass of emissions of a specific greenhouse gas by its equivalent GWP100 factor. The sum of all gases in their CO2e form provide a measure of total greenhouse gas emissions.
  • We see the contribution of different gases to total greenhouse gas emissions. These are measured based on their carbon-dioxide equivalent values. Overall we see that carbon dioxide accounts for around three-quarters of total greenhouse gas emissions. However, both methane and nitrous oxide are also important sources, accounting for around 17 and 7 percent of emissions, respectively.
  • Collectively, HFC, PFC and SF6 are known as the ‘F-gases’. Despite having a very strong warming impact per unit mass (i.e. a high global warming potential), these gases are emitted in very small quantities; they therefore make only a small contribution to total warming.



  • Carbon dioxide is the largest single contributor to human-induced climate change. NASA describes it as ‘the principal control knob that governs the temperature of Earth’. Although other factors (such as other long-lived greenhouse gases, water vapour and clouds) contribute to Earth’s greenhouse effect, carbon dioxide is the dominant greenhouse gas that humans can control in the atmosphere.



  • Scientists have determined that, when all human and natural factors are considered, Earth’s climate balance has been altered towards warming, with the biggest contributor being increases in CO2.



Do Humans Only Affect Climate Change Through Greenhouse Gases?


  • Greenhouse gases emitted by human activities alter Earth’s energy balance and thus its climate.
  • But, humans also affect climate by changing the nature of the land surfaces (for example by clearing forests for farming) and through the emission of pollutants that affect the amount and type of particles in the atmosphere.



Causes Of Climate Change (Sources, Sectors & Countries)

The main driver/cause of climate change is carbon emissions from human activity.

These human activities mainly include the burning of fossil fuels – for vehicles, for electricity generation at power plants and so on.

Water vapour accounts for about half the present-day greenhouse effect, but its concentration in the atmosphere is not influenced directly by human activities. The amount of water in the atmosphere is related mainly to changes in the Earth’s temperature. For example, as the atmosphere warms it is able to hold more water. Although water vapour absorbs heat, it does not accumulate in the atmosphere in the same way as other greenhouse gases; it tends to act as part of a feedback loop rather than being a direct cause of climate change.

So, let’s get more specific about where carbon dioxide comes from according to different sources:

EPA tracks total U.S. emissions by publishing the Inventory of U.S. Greenhouse Gas Emissions and Sinks. This annual report estimates the total national greenhouse gas emissions and removals associated with human activities across the United States.

The primary sources of greenhouse gas emissions in the United States are –

  • Transportation – nearly 28.5 percent of 2016 greenhouse gas emissions
  • Electricity Production – 28.4 percent of 2016 greenhouse gas emissions
  • Industry – 22 percent of 2016 greenhouse gas emissions
  • Commercial and residential – 11 percent of 2016 greenhouse gas emissions
  • Agriculture – 9 percent of 2016 greenhouse gas emissions
  • Land Use And Forestry – offset of 11 percent of 2016 greenhouse gas emissions



Combustible fossil fuels such as coal, power plant gas, oil, vehicles and big industry are the largest source of carbon dioxide. The production is from various items such as iron, steel, cement, natural gas, solid waste combustion, lime, ammonia, limestone, cropland, soda ash, aluminum, petrochemical, titanium and phosphoric acid. Carbon dioxide accounts for nearly 85 percent of all emissions and is produced when natural gas, petroleum and coal are used. The major areas where these fuels are used include electricity generation, transportation, industry and in residential and commercial buildings.



87 percent of all human-produced carbon dioxide emissions come from the burning of fossil fuels like coal, natural gas and oil. The remainder results from the clearing of forests and other land use changes (9%), as well as some industrial processes such as cement manufacturing (4%).

– Further breakdown at


Since the Industrial Revolution there has been a large increase in human activities such as fossil fuel burning, land clearing and agriculture, which affect the release and uptake of carbon dioxide.

According to the most recent Emissions Overview, carbon dioxide and other greenhouse gases are produced in NSW (in Australia) by the following activities or sources:

  • stationary energy sources, such as coal-fired power stations (47 per cent)
  • transport (18 per cent)
  • coal mines (12 per cent)
  • agriculture (11 per cent)
  • land use (7 per cent)
  • land change (3 per cent)
  • waste (2 per cent).

Carbon dioxide released into the atmosphere from burning fossil fuels carries a different chemical fingerprint from that released by natural sources such as respiration and volcanoes. This makes it possible to identify the contribution of human activity to greenhouse gas production.

Data collected by CSIRO show that the concentration of carbon dioxide in our atmosphere in 2018 was approximately 404 parts per million. The level of carbon dioxide in the Earth’s atmosphere is now higher than at any time over the past 800,000—and possibly 20 million—years.

Global atmospheric concentrations of the other greenhouse gases (methane and nitrous oxide) also now exceed pre-industrial values.



Global greenhouse gas emissions can be broken down by sectoral sources in these sections:

  • Energy (energy, manufacturing and construction industries and fugitive emissions): emissions are inclusive of public heat and electricity production; other energy industries; fugitive emissions from solid fuels, oil and gas, manufacturing industries and construction.
  • Transport: domestic aviation, road transportation, rail transportation, domestic navigation, other transportation.
  • International bunkers: international aviation; international navigation/shipping.
  • Residential, commercial, institutional and AFF: Residential and other sectors.
  • Industry (industrial processes and product use): production of minerals, chemicals, metals, pulp/paper/food/drink, halocarbons, refrigeration and air conditioning; aerosols and solvents; semicondutor/electronics manufacture; electrical equipment.
  • Waste: solid waste disposal; wastewater handling; waste incineration; other waste handling.
  • Agriculture: methane and nitrous oxide emissions from enteric fermentation; manure management; rice cultivation; synthetic fertilizers; manure applied to soils; manure left on pasture; crop residues; burning crop residues, savanna and cultivation of organic soils.
  • Land use: emissions from the net conversion of forest; cropland; grassland and burning biomass for agriculture or other uses.
  • Other sources: fossil fuel fires; indirect nitrous oxide from non-agricultural NOx and ammonia; other anthropogenic sources.



Emissions by country…

Cumulative emissions –  As of 2014 – China’s rapid growth in emissions over the last few decades now makes it the world’s second largest cumulative emitter, although it still comes in at less than 50% of the US total.

Annual emissions – In 2014, we can see that a number of low to middle income nations are now within the top global emitters. In fact, China is now the largest emitter, followed by (in order) the US, EU-28, India, Russia, Indonesia, Brazil, Japan, Canada and Mexico. Note that a number of nations that are already top emitters are likely to continue to increase emissions as they undergo development.

In contrast to CO2 emissions growth in low to middle income economies, trends across many high income nations have stabilized, and in several cases decreased in recent decades. Despite this downward trend across some nations, emissions growth in transitioning economies dominates the global trend—as such, global annual emissions have continued to increase over this period.

Per Capita emissions – With a few exceptions, there is an important north-south divide in terms of per capita emissions. Most nations across sub-Saharan Africa, South America and South Asia have per capita emissions below five tonnes per year (many have less than 1-2 tonnes). This contrasts with the global north where emissions are typically above five tonnes per person (with North America above 15 tonnes). The monthly emissions per capita in rich countries are mostly higher than the yearly emissions per capita in poorer countries. The largest emitter, Qatar, has per capita emissions of 50 tonnes per year (1243 times that of Chad, the lowest emitter).

Note that carbon dioxide is not the only greenhouse gas which contributes to climate change—nitrous oxide and methane are also greenhouse gases, but are not included here. Food production, especially intensive livestock-rearing for meat and dairy, is a major contributor to both of these non-CO2 GHGs. Since capita meat intake is strongly linked to GDP levels, per capita emissions of nitrous oxide and methane tend to be much larger in high-income nations.

C02 emissions by source vary depending on the country – we are talking about gas, liquid (i.e. oil), solid (coal and biomass), flaring, and cement production. In the present day, solid and liquid fuel dominate, although contributions from gas production are also notable. Cement and flaring at the global level remain comparably small. has some great missions charts and graphs which show total GHG emissions, as well as Carbon Dioxide, Methane and Nitrous Oxide Emissions by sector, activity, country and more as %’s, parts per million etc. –

You can see the stats, as well as trends of emissions.

The EPA has also outlined each sector where greenhouse gases are emitted. You can read more about those sectors and sources for gases in our guide on solutions to climate change.


Effects Of Climate Change

What is important to note is that there are already some effects that have taken place (such as the rise in temperature, shrinking ice etc.

But, future effects can only be forecasted – but not guaranteed.


Climate change affects the world as a whole, but can also affect different countries, and regions within those countries differently.

There are environmental, social and economic effects.

Some of the current and future effects of climate change are…

  • Warming oceans
  • Shrinking ice sheets
  • Glacial retreat
  • Decreased snow cover
  • Sea level rise
  • Declining Arctic sea ice
  • Extreme events
  • Ocean acidification [due to increased carbon levels]



Global warming and a changing climate have a range of potential ecological, physical and health impacts, including extreme weather events (such as floods, droughts, storms, and heatwaves); sea-level rise; altered crop growth; and disrupted water systems.



  • The enhanced greenhouse effect is expected to change many of the basic weather patterns that make up our climate, including wind and rainfall patterns and the incidence and intensity of storms.
  • Every aspect of our lives is in some way influenced by the climate. For example, we depend on water supplies that exist only under certain climatic conditions, and our agriculture requires particular ranges of temperature and rainfall.



  • Ice is melting in both polar ice caps and mountain glaciers. Lakes around the world, including Lake Superior, are warming rapidly — in some cases faster than the surrounding environment. Animals are changing migration patterns and plants are changing the dates of activity, such as trees budding their leaves earlier in the spring and dropping them later in the fall.
  • There’s an increase in average temperatures and the temperature extremes, there’s extreme weather events, there’s ice melt, there’s sea level rise and acidification, plants and animals are affected, and there are social consequences relating to agriculture, food security and health implication just to name a few.



  • Global effects – hotter days, rising sea levels, more frequent and intense extreme weather events, oceans are warming and acidifying. As humans, every aspect of our life is reliant on the natural environment. This includes the food we eat, the air we breathe, the water we drink, the clothes we wear and the products that are made and sold to create jobs and drive the economy. We need a healthy and stable climate for these things.
  • Country Specific effects such as Australia – temperature rises, water shortages, increased fire threats, drought, weed and pest invasions, intense storm damage and salt invasion.
  • Threatening of the Great Barrier Reef.
  • Animals and plants – One in six species is at risk of extinction because of climate change and habitat destruction and environmental change.
  • Food and Farming – Changes to rainfall patterns, increasingly severe drought, more frequent heat waves, flooding and extreme weather make it more difficult for farmers to graze livestock and grow produce, reducing food availability and making it more expensive to buy.
  • Water – Reduced rainfall and increasingly severe droughts may lead to water shortages.
  • Coastal erosion – Rising sea levels and more frequent and intense storm surges will see more erosion of Australia’s coastline, wearing away and inundating community and residential properties.
  • Health – Increasingly severe and frequent heat waves may lead to death and illness, especially among the elderly. Higher temperatures and humidity could also produce more mosquito-borne disease.
  • Damage to homes – Increasingly severe extreme weather events like bushfires, storms, floods, cyclones and coastal erosion, will see increased damage to homes, as well as more costly insurance premiums.
  • Coral bleaching – Rising temperatures and acidity within our oceans is contributing to extreme coral bleaching events, like the 2016 event that destroyed more than one-third of the Great Barrier Reef.
  • Overall – Within Australia, the effects of global warming vary from region to region.
    The impacts of global warming are already being felt across all areas of Australian life, and these will continue to worsen if we do not act now to limit global warming to 1.5°C.



Future effects might be:

Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.

Scientists have high confidence that global temperatures will continue to rise for decades to come, largely due to greenhouse gases produced by human activities. The Intergovernmental Panel on Climate Change (IPCC), which includes more than 1,300 scientists from the United States and other countries, forecasts a temperature rise of 2.5 to 10 degrees Fahrenheit over the next century.

According to the IPCC, the extent of climate change effects on individual regions will vary over time and with the ability of different societal and environmental systems to mitigate or adapt to change.

The IPCC predicts that increases in global mean temperature of less than 1.8 to 5.4 degrees Fahrenheit (1 to 3 degrees Celsius) above 1990 levels will produce beneficial impacts in some regions and harmful ones in others. Net annual costs will increase over time as global temperatures increase.

“Taken as a whole,” the IPCC states, “the range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time.”

According to the Third and Fourth National Climate Assessment Reports, future effects will be…

  • change through this century and beyond depending on how many greenhouse gases we emit and how sensitive our climate is to them
  • temperatures will continue to rise
  • Frost free season and growing season will lengthen
  • There will be changes in precipitation patterns
  • There will be more droughts and heat waves
  • Hurricanes will become stronger and more intense
  • Sea levels will rise between 1-4 feet by 2100
  • The Arctic is likely to become ice free

NASA also outline the US regional effects so far in Northeast, Northwest, Southeast, Midwest and Southwest. For example, in the Southwest – increased heat, drought and insect outbreaks, all linked to climate change, have increased wildfires. Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns.



Evidence That Climate Change Is A Real Issue, & Is A Direct Cause Of Other Problems

In summary, the main points of evidence are:

  • it has been proved how much of a warming effect greenhouse gases like carbon dioxide have on the earth
  • there was a sharp rise in carbon dioxide levels (in parts per million) since the industrial revolution in the 19th century, and in particular since 1950 – most of it from human activity
  • there was rise in average global earth surface (air) temperature in the same time – compared to pre 1950’s levels
  • there has been a change in other events and things in the same time such as sea levels, ice melting, etc. – compared to pre 1950’s levels


So, you have to be able to prove:

  • Greenhouse gases warm the earth and it’s climate
  • Humans are emitting greenhouse gases at certain levels
  • The GHG’s that human are emitting are causing the warming (as opposed to natural emissions causing it)
  • There are negative side effects of this warming (e.g. sea level rise, ice melt etc.)
  • That this warming and these negative side effects wouldn’t be happening, or happening to the extent they are now without the human caused greenhouse gas emissions (essentially comparing what is happening now with excess emissions, to a baseline without these heavy emissions)
  • Some further information explaining this and evidence is…
  • The finding that the climate has warmed in recent decades and that human activities are producing global climate change has been endorsed by every national science academy that has issued a statement on climate change, including the science academies of all of the major industrialized countries.
  • Scientific consensus is normally achieved through communication at conferences, publication in the scientific literature, replication (reproducible results by others), and peer review. In the case of global warming, many governmental reports, the media in many countries, and environmental groups, have stated that there is virtually unanimous scientific agreement that human-caused global warming is real and poses a serious concern.
  • Several studies of the consensus have been undertaken. Among the most-cited is a 2013 study of nearly 12,000 abstracts of peer-reviewed papers on climate science published since 1990, of which just over 4,000 papers expressed an opinion on the cause of recent global warming. Of these, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused. It is “extremely likely” that this warming arises from “… human activities, especially emissions of greenhouse gases …” in the atmosphere. Natural change alone would have had a slight cooling effect rather than a warming effect.



  • [the current warming trend] is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia.

– IPCC Fifth Assessment Report via


  • For 400,000 years, carbon dioxide levels have never been above 280 to 300 parts per million
  • During ice ages, COlevels were around 200 parts per million (ppm), and during the warmer interglacial periods, they hovered around 280 ppm
  • Around 1950, carbon dioxide levels surpassed 300 parts per million, and as of 2013, levels surpassed 400 parts per million
  • This rise in carbon closely mimics our burning of fossil fuels in the same time. What we know about fossil fuels is that they emit carbon dioxide, and 60 percent of fossil-fuel emissions stay in the air.
  • If fossil-fuel burning continues at a business-as-usual rate, such that humanity exhausts the reserves over the next few centuries, CO2 will continue to rise to levels of order of 1500 ppm. The atmosphere would then not return to pre-industrial levels even tens of thousands of years into the future.



  • The Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.
  • The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia.
  • Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate.
  • The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.
  • Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.
  • Further to this, there are these events tied to the above:
  • Global temperature rise – The planet’s average surface temperature has risen about 1.62 degrees Fahrenheit (0.9 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. Most of the warming occurred in the past 35 years, with the five warmest years on record taking place since 2010. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year — from January through September, with the exception of June — were the warmest on record for those respective months.
  • Warming Oceans – The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.
  • Shrinking Ice Sheets – The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 281 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 119 billion tons during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade.
  • Glacial Retreat – Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.
  • Decreased Snow Cover – Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier.
  • Sea Level Rise – Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century.
  • Declining Arctic Sea Ice – Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.
  • Extreme Events – The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.
  • Ocean Acidification – Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.



  • Look at how the world has warmed since the Industrial Revolution.
  • We see that over the last few decades, temperatures have risen sharply at the global level — to approximately 0.8 degrees celsius higher than our 1961-1990 baseline.
  • When extended back to 1850, we see that temperatures then were a further 0.4 degrees colder than they were in our 1961-1990 baseline.
  • Overall, if we look at the total temperature increase since pre-industrial times, this therefore amounts to approximately 1.2 degrees celcius. We have now surpassed the one-degree mark, an important marker as it brings us more than halfway to the global limit of keeping warming below two degrees celsius.
  • It’s also important to look at trends by hemisphere (North and South), as well as the tropics (defined as 30 degrees above and below the equator).
  • Here we see that the median temperature increase in the North Hemisphere is higher, at closer to 1.4 degrees celcius since 1850, and less in the Southern Hemisphere (closer to 0.8 degrees celcius). Evidence suggests that this distribution is strongly related to ocean circulation patterns (notably the North Atlantic Oscillation) which has resulted in greater warming in the northern hemisphere.



  • Climate change is happening
  • Tens of thousands of scientists in more than a hundred nations have amassed an overwhelming amount of evidence that humans are the cause
  • We are statistically more confident that humans cause climate change than that smoking causes cancer
  • There are nine main independently studied, but physically related, lines of evidence
  • (it is really the first seven that, combined, point to human activities as the only explanation of rising global temperatures since the Industrial Revolution, and the subsequent climate changes (such as ice melt and sea level rise) that have occurred due to this global warming.)
  • Those nine lines of evidence are:
  1. Simple chemistry – when we burn carbon-based materials, carbon dioxide (CO2) is emitted (research beginning in 1900s)
  2. Basic accounting of what we burn, and therefore how much CO2 we emit (data collection beginning in 1970s)
  3. Measuring CO2 in the atmosphere and trapped in ice to find that it is increasing and that the levels are higher than anything we’ve seen in hundreds of thousands of years (measurements beginning in 1950s)
  4. Chemical analysis of the atmospheric CO2 that reveals the increase is coming from burning fossil fuels (research beginning in 1950s)
  5. Basic physics that shows us that CO2 absorbs heat (research beginning in 1820s)
  6. Monitoring climate conditions to find that recent warming of the Earth is correlated to and follows rising CO2 emissions (research beginning in 1930s)
  7. Ruling out natural factors that can influence climate like the sun and ocean cycles (research beginning in 1830s)
  8. Employing computer models to run experiments of natural versus human-influenced simulations of Earth (research beginning in 1960s)
  9. Consensus among scientists who consider all previous lines of evidence and make their own conclusions (polling beginning in 1990s)



  • CO2 keeps the Earth warmer than it would be without it. Humans are adding CO2 to the atmosphere, mainly by burning fossil fuels. And there is empirical evidence that the rising temperatures are being caused by the increased CO2.
  • The reason that the Earth is warm enough to sustain life is because of greenhouse gases in the atmosphere. These gases act like a blanket, keeping the Earth warm by preventing some of the sun’s energy being re-radiated into space. The effect is exactly the same as wrapping yourself in a blanket – it reduces heat loss from your body and keeps you warm. If we add more greenhouse gases to the atmosphere, the effect is like wrapping yourself in a thicker blanket: even less heat is lost.
  • So how can we tell what effect CO2 is having on temperatures, and if the increase in atmospheric CO2 is really making the planet warmer?
  • One way of measuring the effect of CO2 is by using satellites to compare how much energy is arriving from the sun, and how much is leaving the Earth. What scientists have seen over the last few decades is a gradual decrease in the amount of energy being re-radiated back into space. In the same period, the amount of energy arriving from the sun has not changed very much at all. This is the first piece of evidencemore energy is remaining in the atmosphere.
  • The primary greenhouse gases – carbon dioxide (CO2), methane (CH4), water vapour, nitrous oxide and ozone – comprise around 1% of the air. This tiny amount has a very powerful effect, keeping the planet 33°C (59.4°F) warmer than it would be without them. (The main components of the atmosphere – nitrogen and oxygen – are not greenhouse gases, because they are virtually unaffected by long-wave, or infrared, radiation). This is the second piece of evidencea provable mechanism by which energy can be trapped in the atmosphere
  • We now look at the amount of CO2 in the air. We know from bubbles of air trapped in ice cores that before the industrial revolution, the amount of CO2 in the air was approximately 280 parts per million (ppm). In June 2013, the NOAA Earth System Research Laboratory in Hawaii announced that, for the first time in thousands of years, the amount of CO2 in the air had gone up to 400ppm. That information gives us the next piece of evidenceCO2 has increased by nearly 43% in the last 150 years.
  • The final piece of evidence is ‘the smoking gun’, the proof that CO2 is causing the increases in temperature. CO2 traps energy at very specific wavelengths, while other greenhouse gases trap different wavelengths.  In physics, these wavelengths can be measured using a technique called spectroscopy. When looking at the different wavelengths of energy, measured at the Earth’s surface, on a Spectroscopy Graph – among the spikes you can see energy being radiated back to Earth by ozone (O3), methane (CH4), and nitrous oxide (N20). But the spike for CO2 dwarfs all the other greenhouse gases, and tells us something very important: most of the energy being trapped in the atmosphere corresponds exactly to the wavelength of energy captured by CO2.
  • To sum up:
  • 1. What is happening – More energy is remaining in the atmosphere on Earth
  • 2. How is this happening – Greenhouse gases are the mechanism by which energy is trapped in the atmosphere
  • 3. Why is this happening – CO2 has increased by nearly 50% in the last 150 years and the increase is from burning fossil fuels
  • 4. Linking the tw0 – energy being trapped in the atmosphere corresponds exactly to the wavelengths of energy captured by CO2
  • This is empirical evidence that proves, step by step, that man-made carbon dioxide is causing the Earth to warm up.



  • The science on the human contribution to modern warming is quite clear. Humans emissions and activities have caused around 100% of the warming observed since 1950
  • Since 1850, almost all the long-term warming can be explained by greenhouse gas emissions and other human activities.
  • If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred. They are offset by cooling from human-produced atmospheric aerosols.
  • Aerosols are projected to decline significantly by 2100, bringing total warming from all factors closer to warming from greenhouse gases alone.
  • Natural variability in the Earth’s climate is unlikely to play a major role in long-term warming.
  • Some of the findings that back up these results are…
  • Greenhouse gas forcings match actual observed global surface temperature warming – Scientists measure the various factors that affect the amount of energy that reaches and remains in the Earth’s climate. They are known as “radiative forcings”. They can be natural (such as volcanoes) and man made (such as greenhouse gases). When looking at a graph that shows the estimated role of each different climate forcing in changing global surface temperatures since records began in 1850, of all the radiative forcings analysed, only increases in greenhouse gas emissions produce the magnitude of warming experienced over the past 150 years.
  • Human forcings match actual observed global surface temperature warmings
  • Land temperatures are rising faster now – Land temperatures have warmed considerably faster than average global temperatures over the past century, with temperatures reaching around 1.7C above pre-industrial levels in recent years.
  • From the models, future forecasts are that land warms by around 4C by 2100 compared to 3C globally for surface temperature
  • While human factors explain all the long-term warming, there are some specific periods that appear to have warmed or cooled faster than can be explained based on our best estimates of radiative forcing.
  • Short term warming or cooling may occur via natural factors, but long term natural variability to impact long-term warming trends is extremely unlikely
  • Internal variability is likely to have a much larger role in regional temperatures. For example, in producing unusually warm periods in the Arctic and the US in the 1930s.
  • In summary – While there are natural factors that affect the Earth’s climate, the combined influence of volcanoes and changes in solar activity would have resulted in cooling rather than warming over the past 50 years. The global warming witnessed over the past 150 years matches nearly perfectly what is expected from greenhouse gas emissions and other human activity, both in the simple model examined here and in more complex climate models. The best estimate of the human contribution to modern warming is around 100% . Some uncertainty remains due to the role of natural variability, but researchers suggest that ocean fluctuations and similar factors are unlikely to be the cause of more than a small fraction of modern global warming.

– answers many climate change related questions that give evidence of the link between greenhouse gases and climate change at

These questions and answers include:

    • Is the climate warming (lists the range of observations, indications and evidence that show warming has occured)
    • How do scientists know that recent climate change is largely caused by human activities?
    • CO2 is already in the atmosphere naturally, so why are emissions from human activity significant?
    • What role has the Sun played in climate change in recent decades?
    • What do changes in the vertical structure of atmospheric temperature – from the surface up to the stratosphere – tell us about the causes of recent climate change?
    • Climate is always changing. Why is climate change of concern now?
    • Is the current level of atmospheric CO2concentration unprecedented in Earth’s history?
    • Is there a point at which adding more CO2 will not cause further warming?
    • Does the rate of warming vary from one decade to another?
    • Does the recent slowdown of warming mean that climate change is no longer happening?
    • If the world is warming, why are some winters and summers still very cold?
    • Why is Arctic sea ice reducing while Antarctic sea ice is not?
    • How does climate change affect the strength and frequency of floods, droughts, hurricanes and tornadoes?
    • How fast is sea level rising?
    • What is ocean acidification and why does it matter?
    • How confident are scientists that Earth will warm further over the coming century?
    • Are climate changes of a few degrees a cause for concern?
    • What are scientists doing to address key uncertainties in our understanding of the climate system?
      • Are disaster scenarios about tipping points like ‘turning off the Gulf Stream’ and release of methane from the Arctic a cause for concern?
    • If emissions of greenhouse gases were stopped, would the climate return to the conditions of 200 years ago?



Climate Change Evidence Stats

C02 & Other Greenhouse Gas Level Changes

The global mean CO2 level in 2013 was 395 parts per million. This concentration represents a 43 per cent increase from pre-industrial levels; it is likely to be at the highest concentration in at least 2 million years.

Methane and nitrous oxide concentrations, mostly from agriculture, have increased by 150% and 20% respectively since 1750.



Records of air bubbles in ancient Antarctic ice show us that carbon dioxide and other greenhouse gases are now at their highest concentrations for more than 800,000 years.



Global Surface Temperature Change

We have tracked significant increase in global temperatures of at least 0.85°C and a sea level rise of 20cm over the past century.



You can check out global temperature change at 


Global Sea Level Change

We have tracked significant increase in global temperatures of at least 0.85°C and a sea level rise of 20cm over the past century.



You can check out global sea level at 


Average Sea Surface Temperature Change

You can check out average sea surface temperature which is rising at


Looking At Evidence Overall

Overall, you can’t just look at temperature (air temperature, land temperature, water temperature) to diagnose or assess climate change. You also have to look at sea levels, ocean acidity, ice sheets, ecosystem trends, and other factors to get a well rounded answer.


Ways To Monitor The Impact Climate Change Is Having Now & Into The Future

Some of the long-term effects of global climate change in the United States are listed in the Third and Fourth National Climate Assessment Reports.

But, NASA list some of the effects and expected effects of climate change at

(Some effects that scientists had predicted in the past would result from global climate change are now occurring: loss of sea ice, accelerated sea level rise and longer, more intense heat waves.)

Among the impacts to look out for and monitor and link to each other are:

  • Continued C02 parts per million levels rising
  • Continued earth air surface temperature rising
  • Land temperature rising
  • Ocean temperatures rising
  • Glaciers shrinking
  • Ice on rivers and lakes breaking up earlier
  • Plant and animal ranges shifting
  • Trees and plants flowering sooner
  • Loss of sea ice
  • Accelerated sea level rise
  • Longer, more intense heat waves
  • Frost free and growing seasons lengthening (The largest increases in the frost-free season (more than eight weeks) are projected for the western U.S., particularly in high elevation and coastal areas.)
  • Changes in precipitation patterns – trend towards increased heavy precipitation events
  • More droughts, heat waves and hot days (By the end of this century, what have been once-in-20-year extreme heat days (one-day events) are projected to occur every two or three years over most of the nation.)
  • Cold waves to become less intense
  • Hurricanes becoming stronger and more intense (The intensity, frequency and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain)
  • Sea levels to rise (Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.)
  • Land subsidence to increase (land sinking)
  • Flooding of coastal and sea side land to increase
  • Arctic Ocean to become ice free
  • Infrastructure, agriculture, fisheries and ecosystems will be increasingly compromised
  • Increasing wildfire, insect outbreaks and tree diseases
  • Increasing ocean acidity
  • Decreased freshwater availability
  • Increased erosion



Debate & Disagreement Over Climate Change & Global Warming

You can read more about the debate and controversy over climate change and it’s impact/effects at 


Answers To Skeptical Arguments Against Climate Change

Skeptical Science has a good resource answering common skeptical arguments against climate change:



How Are C02 Concentrations Obtained In Current Time, & From The Past?

More recently, there are observatories that measure air CO2 levels.

But, historic CO2 levels can be found in ice cores, and also rock sediment samples from the ocean and lakes.

There are other ancient samples (such as tree rings, studying ancient organisms etc.) that can also be used to get an idea of CO2 levels from the past.

Read more about how climate change indicators and past CO2 levels are measured in this guide.


Climate Change & Trade/Import Between Developed vs Developing Countries

  • Climate change can lead to lead to widespread drought, disease and desperation in some of the world’s poorest regions
  • Migration by refugees affected by climate change is predicted in the future
  • Richer nations have a lot of carbon emissions contained in the products and materials they import from developing countries
  • Of the carbon emissions that European consumers are personally responsible for, around 22% are allocated elsewhere under conventional carbon accounting practices. For consumers in the US, the figure is around 15%.
  • Heavy industry and the constant demand for consumer goods are key contributors to climate change
  • 30% of global greenhouse gas emissions are produced through the process of converting metal ores and fossil fuels into the cars, washing machines and electronic devices that help prop up richer economies
  • Richer nations have more purchasing power and through their consumption of products, contribute to emissions and pollution
  • For every item bought or sold there is a rise in GDP, and with each 1% increase in GDP there is a corresponding 0.5 to 0.7% rise in carbon emissions
  • For metal ores alone, the extraction rate more than doubled between 1980 and 2008
  • Every time you buy a new car, for instance, you effectively mine 3-7g of “platinum group metals” to coat the catalytic converter. The six elements in the platinum group have the greatest environmental impact of all metals, and producing just one kilo requires the emission of thousands of kilos of CO₂
  • This is only one example of the toll poorer countries are taking to satisfy richer countries
  • The problem is that in poorer countries choose to accept this behavior for a variety of factors, and citizens see it as the only way to get out of poverty (because it provides jobs)
  • Richer nations must start implementing sustainable material strategies that address a product’s entire lifecycle from mining to manufacturing, use, and eventually to disposal. They must consider the well being of the people and environment in the countries they are importing from
  • Consumers can also vote with their dollars and buy from more ethical and sustainable countries



Potential Climate Change Solutions (Mitigation, Adaptation, Carbon Sequestering)

The best solution is to bring emissions to zero as soon as possible.

But, realistically – there is going to need to be a different approach to doing that in each industry and sector of society.

Two big examples are – renewable energy sources in the electricity generation sector, and cleaner cars in the transport sector.

There needs to be an approach that considers employment, the economy and practicality right now, and the future environmental needs of the future.

Building infrastructure, getting funding, transferring to new technologies and power sources – all take time and have technical challenges – so it’s something that requires serious planning and research as to how to best do it.


Some specific solutions might include:

  • More efficient use of residential electronics, and new technology for household electronics
  • More efficient use of residential appliances
  • Retrofit residential HVAC
  • Tillage and residue management
  • Insulation retrofits for residential
  • Hybrid cars
  • Waste recycling
  • Lighting – switch from incandescent to LED lights (residential)
  • Retrofit insulation (commercial)
  • Better motor systems efficiency
  • Cropland nutrient management
  • Clinker substitution by fly ash
  • Electricity from landfill gas
  • Efficiency improvements by different industries
  • Rice management
  • 1st generation biofuels
  • Small hydro
  • Reduced slash and burn agriculture conversion
  • Reduced pastureland conversion
  • Grassland management
  • Geothermal energy
  • Organic soil restoration
  • Building energy efficiency in new builds
  • 2nd gen biofuels
  • Degraded land restoration
  • Pastureland afforestation
  • Nuclear energy
  • Degraded forest reforestation
  • Low penetration wind technology and energy
  • Solar CSP technology and energy
  • Solar PV technology and energy
  • High penetration wind technology and energy
  • Reduced intensive agriculture conversion
  • Power plant biomass co-firing
  • Coal CCS new build
  • Iron and steel CCS new build
  • Coal CCS retrofit
  • Gas plant CCS retrofit



Also according to

  • To keep global temperature rise below the agreed 2°C, global carbon emission must peak in the next decade and from 2070 onward must be negative
  • The goal, with the Paris Agreement in mind, is limiting warming to 2℃ above pre-industrial levels. The Paris Agreement went further, aiming to “pursue efforts” towards a more ambitious goal of just 1.5℃. Given we’re already at around 1℃ of warming, that’s a relatively short-term goal.
  • The warming will slow to a potentially manageable pace only when human emissions are reduced to zero. The good news is that they are now falling in many countries as a result of programs like fuel-economy standards for cars, stricter building codes and emissions limits for power plants. But experts say the energy transition needs to speed up drastically to head off the worst effects of climate change
  • The energy sources with the lowest emissions include wind turbines, solar panels, hydroelectric dams and nuclear power stations. Power plants burning natural gas also produce fewer emissions than those burning coal. Using renewables can be costlier in the short term
  • Burning gas instead of coal in power plants reduces emissions in the short run, though gas is still a fossil fuel and will have to be phased out in the long run
  • “Clean coal” is an approach in which the emissions from coal-burning power plants would be captured and pumped underground. It has yet to be proven to work economically, but some experts think it could eventually play a major role.



Mitigation of climate change are actions to reduce greenhouse gas emissions, or enhance the capacity of carbon sinks to absorb greenhouse gases from the atmosphere.

There is a large potential for future reductions in emissions by a combination of activities, including energy conservation and increased energy efficiency; the use of low-carbon energy technologies, such as renewable energy, nuclear energy, and carbon capture and storage; and enhancing carbon sinks through, for example, reforestation and preventing deforestation.

A 2015 report by Citibank concluded that transitioning to a low carbon economy would yield positive return on investments.

Apart from mitigation, adaptation and climate engineering are other options for responses.



Cost Of Pursuing Climate Change Mitigation

According to OurWorldInData, these are very loose and very roughly estimated costs to pursue climate change mitigation. These costs have lots of variables:

The possible cost-benefit of taking global and regional action on climate change is often a major influencing factor on the effectiveness of mitigation agreements and measures.

If we aggressively pursue all of the low-cost abatement opportunities currently available, the total global economic cost would be €200-350 billion per year by 2030. This is less than one percent of the forecasted global GDP in 2030.

If we include these additional opportunities, our maximum technical abatement potential by 2030 totals 47 billion tonnes of CO2e per year. Our maximum global potential is therefore a 65-70% reduction relative to our current projected pathway.



Recent Greenhouse Gas Trends (Total Greenhouse Gas Emissions)

Since 1990, gross U.S. greenhouse gas emissions have increased by about 2 percent. From year to year, emissions can rise and fall due to changes in the economy, the price of fuel, and other factors.

In 2016, U.S. greenhouse gas emissions decreased compared to 2015 levels. This decrease was largely driven by a decrease in emissions from fossil fuel combustion, which was a result of multiple factors including substitution from coal to natural gas consumption in the electric power sector; warmer winter conditions that reduced demand for heating fuel in the residential and commercial sectors.

You can see total US GHG emissions between 1990 and 2016 at



EPA also shows the total global and national GG emissions by %:

  • National –
  • Global –

In the US you can see carbon dioxide emissions have been gradually decreasing since around 2007 to 2016.


Forecast For Climate Change Into The Future

Climate change and it’s effects can be forecasted into the future, but not with an absolute guarantee (some forecasts from the past weren’t completely accurate).

There variables that can impact how quickly warming takes place, and how the earth and different indicators in different parts of the world react.

Climate models can forecast for 100’s of different scenarios based on these variables.

There may be warming in some parts of the world, and there may be cooling in others just as one example.

It’s more realistic to be aware of the indicators and causes, understand what potential future scenarios might be, and continue to monitor them and adjust expectations accordingly.

What most experts do agree on though is that it’s in our best interests to decrease human GHG emissions as soon as possible.



  • The continued burning of fossil fuels will inevitably lead to further climate warming. The complexity of the climate system is such that the extent of this warming is difficult to predict, particularly as the largest unknown is how much greenhouse gas we keep emitting.
  • The IPCC has developed a range of emissions scenarios or Representative Concentration Pathways (RCPs) to examine the possible range of future climate change.
  • Using scenarios ranging from business-as-usual to strong longer-term managed decline in emissions, the climate model projections suggest the global mean surface temperature could rise by between 2.8°C and 5.4°C by the end of the 21st century. Even if all the current country pledges submitted to the Paris conference are achieved we would still only just be at the bottom end of this range.
  • The sea level is projected to rise by between 52cm and 98cm by 2100, threatening coastal cities, low-lying deltas and small island nations. Snow cover and sea ice are projected to continue to reduce, and some models suggest that the Arctic could be ice-free in late summer by the latter part of the 21st century.
  • Heat waves, droughts, extreme rain and flash flood risks are projected to increase, threatening ecosystems and human settlements, health and security. One major worry is that increased heat and humidity could make physical work outside impossible.
  • Changes in precipitation are also expected to vary from place to place. In the high-latitude regions (central and northern regions of Europe, Asia and North America) the year-round average precipitation is projected to increase, while in most sub-tropical land regions it is projected to decrease by as much as 20%, increasing the risk of drought.
  • In many other parts of the world, species and ecosystems may experience climatic conditions at the limits of their optimal or tolerable ranges or beyond.
  • Human land use conversion for food, fuel, fibre and fodder, combined with targeted hunting and harvesting, has resulted in species extinctions some 100 to 1000 times higher than background rates. Climate change will only speed things up.
  • This is the challenge our world leaders face. To keep global temperature rise below the agreed 2°C, global carbon emission must peak in the next decade and from 2070 onward must be negative: we must start sucking out carbon dioxide from the atmosphere.
  • Despite 30 years of climate change negotiations there has been no deviation in greenhouse gas emissions from the business-as-usual pathway, so many feel keeping global warming to less than 2°C will prove impossible.
  • Previous failures, most notably at Copenhagen in 2009, set back meaningful global cuts in emissions by at least a decade. Paris, however, offers a glimmer of hope.



  • Near- and long-term trends in the global energy system are inconsistent with limiting global warming at below 1.5 or 2 °C, relative to pre-industrial levels. Pledges made as part of the Cancún agreements are broadly consistent with having a likely chance (66 to 100% probability) of limiting global warming (in the 21st century) at below 3 °C, relative to pre-industrial levels.



What does the future of our carbon dioxide and greenhouse gas emissions look like? [here are] … a range of potential future scenarios of global greenhouse gas emissions (measured in gigatonnes of carbon dioxide equivalents), based on data from Climate Action Tracker. Here, five scenarios are shown:

  • No climate policies: projected future emissions if no climate policies were implemented; this would result in an estimated 4.1-4.8°C warming by 2100 (relative to pre-industrial temperatures)
  • Current climate policies: projected warming of 3.1-3.7°C by 2100 based on current implemented climate policies
  • National pledges: if all countries achieve their current targets/pledges set within the Paris climate agreement, it’s estimated average warming by 2100 will be 2.6-3.2°C. This will go well beyond the overall target of the Paris Agreement to keep warming “well below 2°C”.
  • 2°C consistent: there are a range of emissions pathways that would be compatible with limiting average warming to 2°C by 2100. This would require a significant increase in ambition of the current pledges within the Paris Agreement.
  • 1.5°C consistent: there are a range of emissions pathways that would be compatible with limiting average warming to 1.5°C by 2100. However, all would require a very urgent and rapid reduction in global greenhouse gas emissions.



Climate Change Overall Is A Complex Process – It Has Drivers, Amplifiers, Diminishers & Feedbacks That All Interact With Each Other

Based just on the physics of the amount of energy that CO2 absorbs and emits, a doubling of atmospheric CO2 concentration from pre-industrial levels (up to about 560 ppm) would, by itself, cause a global average temperature increase of about 1 °C (1.8 °F).

In the overall climate system, however, things are more complex; warming leads to further effects (feedbacks) that either amplify or diminish the initial warming.

The most important feedbacks involve various forms of water.

A warmer atmosphere generally contains more water vapour.

Water vapour is a potent greenhouse gas, thus causing more warming; its short lifetime in the atmosphere keeps its increase largely in step with warming. Thus, water vapour is treated as an amplifier, and not a driver, of climate change.

Higher temperatures in the polar regions melt sea ice and reduce seasonal snow cover, exposing a darker ocean and land surface that can absorb more heat, causing further warming.

Another important but uncertain feedback concerns changes in clouds. Warming and increases in water vapour together may cause cloud cover to increase or decrease which can either amplify or dampen temperature change depending on the changes in the horizontal extent, altitude, and properties of clouds.

The latest assessment of the science indicates that the overall net global effect of cloud changes is likely to be to amplify warming.

The ocean moderates climate change. The ocean is a huge heat reservoir, but it is difficult to heat its full depth because warm water tends to stay near the surface. The rate at which heat is transferred to the deep ocean is therefore slow; it varies from year to year and from decade to decade, and helps to determine the pace of warming at the surface.

Observations of the sub-surface ocean are limited prior to about 1970, but since then, warming of the upper 700 m (2,300 feet) is readily apparent. There is also evidence of deeper warming.

Surface temperatures and rainfall in most regions vary greatly from the global average because of geographical location, in particular latitude and continental position.

Both the average values of temperature, rainfall, and their extremes (which generally have the largest impacts on natural systems and human infrastructure), are also strongly affected by local patterns of winds.

Estimating the effects of feedback processes, the pace of the warming, and regional climate change requires the use of mathematical models of the atmosphere, ocean, land, and ice (the cryosphere) built upon established laws of physics and the latest understanding of the physical, chemical and biological processes affecting climate, and run on powerful computers.

Models vary in their projections of how much additional warming to expect (depending on the type of model and on assumptions used in simulating certain climate processes, particularly cloud formation and ocean mixing), but all such models agree that the overall net effect of feedbacks is to amplify warming.



Other Notes & Stats On Climate Change, C02 & Greenhouse Emissions

C02 and Economic development

Historically, CO2 emissions have been primarily driven by increasing fuel consumption. This energy driver has been, and continues to be, a fundamental pillar of economic growth and poverty alleviation. As a result, there is a strong correlation between per capita CO2 emissions and GDP per capita for countries.

There are also noticeable within-country inequalities in greenhouse gas emissions



C02 and Poverty alleviation

The link between economic growth and CO2 described above raises an important question: do we actually want the emissions of low-income countries to grow despite trying to reduce global emissions? In our historical and current energy system (which has been primarily built on fossil fuels), CO2 emissions have been an almost unavoidable consequence of the energy access necessary for development and poverty alleviation.

In general, we see a very similar correlation in both CO2 and energy: higher emissions and energy access are correlated to lower levels of extreme poverty. Energy access is therefore an essential component in improved living standards and poverty alleviation.

In an ideal world, this energy could be provided through 100% renewable energy: in such a world, CO2emissions could be an avoidable consequence of development. However, currently we would expect that some of this energy access will have to come from fossil fuel consumption (although potentially with a higher mix of renewables than older industrial economies). Therefore, although the global challenge is to reduce emissions, some growth in per capita emissions from the world’s poorest countries remains a sign of progress in terms of changing living conditions and poverty alleviation.



C02 Intensity Of Economies 

If economic growth is historically linked to growing CO2 emissions, why do countries have differing levels of per capita CO2 emissions despite having similar GDP per capita levels? These differences are captured by the differences in the CO2 intensity of economies; CO2 intensity measures the amount of CO2 emitted per unit of GDP (kgCO2 per int-$). There are two key variables which can affect the CO2 intensity of an economy:

  • Energy efficiency: the amount of energy needed for one unit of GDP output. This is often related to productivity and technology efficiency, but can also be related to the type of economic activity underpinning output. If a country’s economy transitions from manufacturing to service-based output, less energy is needed in production, therefore less energy is used per unit of GDP.
  • Carbon efficiency: the amount of CO2 emitted per unit energy (grams of CO2 emitted per kilowatt-hour). This is largely related to a country’s energy mix. An economy powered by coal-fired energy will produce higher CO2 emissions per unit of energy versus an energy system with a high percentage of renewable energy. As economies increase their share of renewable capacity, efficiency improves and the amount of CO2 emitted per unit energy falls.

Global CO2 intensity has been steadily falling since 1990.17 This is likely thanks to both improved energy and technology efficiency, and increases in the capacity of renewables. The carbon intensity of nearly all national economies has also fallen in recent decades. Today, we see the highest intensities in Asia, Eastern Europe, and South Africa. This is likely to be a compounded effect of coal-dominated energy systems and heavily industrialized economies.



C02 Intensity and Prosperity 

On average, we see low carbon intensities at low incomes; carbon intensity rises as countries transition from low-to-middle incomes, especially in rapidly growing industrial economies; and as countries move towards higher incomes, carbon intensity falls again.



C02 intensity of goods imported and exported by country

Some countries take on emissions via trade.

The net emissions transfers here is the COembedded in imported goods minus the COembedded in exported goods. This tells us whether a country is a net exporter or importer of emissions.

Based on the updated data gathered by Peters et al. (2012) and the Global Carbon Project, if we switched to a consumption-based reporting system (which corrects for this trade), in 2014 the annual CO2 emissions of many European economies would increase by more than 30% (the UK by 38%; Sweden by 66%; and Belgium’s emissions would nearly double); and the USA’s emissions would increase by 7%.

On the other hand, China’s emissions would decrease by 13%; India’s by 9%; Russia’s by 14% and South Africa by 29%. The goods exported from Russia, China, India, and the Middle East typically have a high carbon intensity, reflecting the fact that their exports are often manufactured goods.

In contrast, we see that exports from the UK, France, Germany and Italy are low; this is likely to be the higher share of export of service-based exports relative to those produced from heavy industry.

Production vs consumption based emissions – If a country’s consumption-based emissions are higher than its production-based emissions then it is a net importer of CO2. If production-based emissions are higher, it is a net exporter.






3. Hannah Ritchie and Max Roser (2018) – “CO₂ and other Greenhouse Gas Emissions”. Published online at Retrieved from: ‘’ [Online Resource]































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