Although there is a consensus about climate change, there are those that debate the entire concept, or at least parts of climate science.
From all the research we have done, rather than using one statement to explain climate change, it can be far more clear and lead to far more understanding to divide the various sub topics and conclusions into categories.
In this guide, we categorise:
- what we do know about climate change (and there is essentially no debate over)
- what we think we know about climate change (but there can be debate over)
- what we are giving our best researched estimate or forecast about, but admit there might also be some uncertainty about
- followed by a summary
Summary – What Is Our Best Conclusion About Climate Change Right Now?
- The term climate change might confuse and divide some people
- Instead – we can focus on what we do and don’t know, as well as what we might know about the issue
- What we do know for sure is that the Earth’s global average surface temperature has increased over the last century and a bit
- We know that greenhouse gas emissions are one cause of global warming
- We know that the levels of carbon dioxide in the air haven’t been this high since humans inhabited the Earth, but may have been higher in times before humans were on Earth
- We know that we have measured other environmental and climate based effects int the last century with improving technology such as satellites (before this time – we have to rely on ice cores, rock sediments, and other less reliable or more uncertain data)
- Our best guess, based on all the current data available, as well as climate modelling to help us make informed guesses, is that human caused greenhouse gas emissions are the main cause of the warming we are seeing
- We can’t say for sure how much the levels of human greenhouse gas emissions and climate increase are linked to the environmental and other observations we are measuring and reporting
- One example of climate modelling is with the Cape Town water shortage caused in part by severe droughts and decreased rainfall. Some climate modelling suggests the 1 degree of warming we have already experienced made the severe drought experience up to three times more likely (theconversation.com)
- Some people argue that the models made for climate change forecasts, and linking certain events to increase global average surface temperature, are uncertain and lack a certain amount of accuracy – which is a valid point. But, the data and evidence gathered on our warming climate goes much deeper and wider than just these models, and all this data needs to be taken as a whole.
- Climate modelling isn’t perfect – it’s one way of feeding the data we do have into a calculation and getting a calculated guess on what might be happening or what might happen in the future
- There are many variables that determine where our climate might go in the future, that good scientists freely admit produce uncertainty in future predictions. Good scientists also admit some level of uncertainty in ancient forms of climate data before we had modern data and measuring equipment
- What we think we know, is that our best informed guess to minimise climate change in the future to less than 1.5C, would require annual emissions to fall by about 50% between now and 2030, and reach net zero by 2050 (theguardian.com). If we are able to decrease CO2 emissions to zero by the year 2080, we might avoid 2℃ of global temperature increase, but would pass 1.5℃ before the year 2040.
- Carbon budgets (how many tonnes of carbon we can emit before reaching a certain temperature) have been revised in the past, so there are differing opinions on what level of warming we might reach as a maximum in the future based on current levels of emissions. Anywhere from 3 degrees up to 4.8 degrees is predicted by the end of the century (year 2100) with no emissions policies, or current emission policies in place. Better reductions and sequestering may obviously lower that
- As well as carbon emissions reductions, carbon sequestration (by planting more trees and vegetation) is also a strategy
- We do know for sure that China is the biggest coal user and greenhouse gas emitter right now. The US is the second biggest GHG emitter. So, the biggest improvements might come from these countries
- We also know for sure that we will have to choose ways to adapt to climate change and increasing temperatures – even, if we can’t agree on what the main cause of climate change is. To illustrate this, we know for sure that rising temperatures impact the natural fresh water cycle, and agricultural growing seasons. We must put in place measures to have affordable and abundant fresh water and food available in the future – these are only two examples though.
- Some climate change supporters admit that it is the risk that human greenhouse emissions are the main cause of warming that is the issue (which needs to have risk mitigation put in place for – because of the potential consequences of not protecting against this risk), rather than human GHGs being an absolute certainty for the main cause of the warming we are seeing
- One example of a potentially catastrophic scenario we might face if we don’t address the downside of the risk, is that we reach a level of warming where natural feedback loops amplify that warming with a continual compounding pattern, and the amount of greenhouse gases we emit no longer allows us to limit warming
- For those that use the main argument Earth’s climate has changed before to argue human emissions are not the main cause of the current change we are seeing – this article might be essential reading – https://skepticalscience.com/climate-change-little-ice-age-medieval-warm-period-intermediate.htm
- Having said that, there are people on one side or the other strongly, as well as those in between
- Another thing to note is that some of the main solutions being suggested are changing to renewable energy from the current burning of fossil fuels for fuel and energy production – particularly in energy generation and transport sectors. On a non climate related note – this makes practical sense as fossil fuel reserves will eventually run out (they are finite), become expensive to mine, and they cause a range of air pollution (via the release of air contaminants) and other environmental issues (such as the damage done by mining operations). Also, carbon dioxide in the air is absorbed by the ocean, leading to warming of parts/layers of the water, altering of the ocean’s chemistry and decreasing the pH of the surface water (killing off coral and other marine life, amongst other impacts). So, some of the solutions being proposed for climate change have many more benefits beyond just global warming and temperature increase as an issue
What We Do Know (For Sure) About Climate Change
- the average global surface temperature has increased about 0.9 degrees celcius since 1880 (but, this does not mean the temperature is rising everywhere, or that the average temperature rise is responsible for every significant weather event)
- the atmospheric concentration of carbon dioxide has risen steadily since humans began to use large quantities of coal during the Industrial Revolution (the atmosphere has now reached levels of carbon dioxide that have never been seen in the history of human civilization, but might have been seen before humans walked on the Earth)
- we know that greenhouse gases cause the Earth to warm via the greenhouse effect (carbon dioxide is a greenhouse gas, along with methane and other gases), and that GHG emissions from humans adds to the concentration of gases in the atmosphere
- we know that in addition to man made factors, there are natural factors that can contribute to warming and cooling of the Earth
- we know that the Earth has warmed, and even gotten colder in the past
- sea levels have risen about 5 to 8 inches since 1900, due to warm water expanding and glaciers melting – this results in a partial loss of some coastlines, and the loss of some islands
- other significant environmental changes and events have been observed and measured
So, we know the Earth is warming in some ways, and we know that greenhouse gases warm the earth via the greenhouse gas effect (trapping and reflecting heat back at the Earth’s surface).
What We Think We Know About Climate Change (But There Can Be Some Debate Over)
- There is a scientific consensus (about 97%) that emissions from humans are the main cause of the warming trend we have seen since the start of industrial times, and not natural factors
So, we are pretty sure that humans (and not natural factors – at least, over the long term of more than a decade) are the most likely cause of the warming effect we are seeing in the present time.
What We Might Make An Educated Guess About With Climate Change, But There Is Varying Uncertainty Over
- What future emissions will be
- How much more warming will occur
- What the exact impact of this warming will be, and what significant weather or environmental events are a result of this warming (or had the likelihood increased by the warming)
- How earth’s feedback loop will react to more warming
- How sensitive earth’s climate is to emissions
- How much impact natural forcings are having over short time spans up to 10 years (compared to longer time spans like decades, centuries, and 1000’s of years)
- How climate change will impact regional climates – regional climate change is much harder to predict than global change
- How exactly water vapour and ice feedbacks, ocean circulation changes, and natural cycles of greenhouse gases will impact climate change
- How accurate or complete past/historical climate data (before new age climate monitoring and measurements) can be e.g. ice cores and rock sediments samples. Prior to modern climate measurement technology like when the climate change observatory was set up, and satellite technology provided modern monitoring and data collection, previous data and measurements can pale in comparison
- When abrupt (sudden) climate change events might happen
- How reliable the emissions reports of different countries are
- How much carbon different types of coal emits
- How accurate and reliable different climate models and calculations are (the data you feed into them, the assumptions they make, and other factors, can all impact the forecast or result the model produces)
Read more about uncertainties to do with climate change in this guide
Based on the data and modelling we have available to us, one guess as to the warming that might take place in the future is:
- If there were no technological or policy changes to reduce emission trends from their current trajectory, then further warming of 2.6 to 4.8 °C (4.7 to 8.6 °F) in addition to that which has already occurred (about 0.9 °C has already occured) would be expected during the 21st century.
A more official resource outlining what we do know, what we probably know, and what we might be uncertain about in regards to climate change can be found at http://www.probeinternational.org/RS_ClimateChange_SummaryofScience.pdf