Measuring and observing climate change and global warming is a multi-faceted process.
You can’t just look at one indicator or measurement, such as the amount of carbon dioxide in the air for example.
There are a range of data sets to collect, a range of indicators to track and monitor, and impacts and effects to observe from the past, in the present, and into the future.
By putting all this data and these events together – a clearer idea of the complete picture of climate change and global warming can be formulated.
Measuring and monitoring technology and instruments have also advanced (particularly within the last few decades) to make the job easier and more accurate.
In this guide, we look at some of the things scientists measure, how they might measure them, and things that might be observed as warming continues.
Summary: How Climate Change & Global Warming Is Measured & Observed
Climate is measured
- in real time or the present (direct evidence), and
- indirect evidence can also be obtained for clues about what the climate looked like in earth’s past.
With direct evidence, monitoring and measuring has advanced in the 20th and 21st centuries from simple thermometers and rain gauges, to measurements with electronic satellites, instruments and sensors, and other more advanced technology.
Indirect measurements might include ice cores or sediment samples.
When taking climate change measurements, there’s a distinction to be made between global and regional measurements.
It should also be noted that different tests and measurements are taken for a range of climate indicators.
For example, temperature might be measured with a thermometer, whereas carbon levels in the ocean might be measured with satellites and buoys. These are just two of many examples.
How Climate Scientists Might Measure And Obtain Different Data
For many thousands and millions of years ago (looking at carbon dioxide bubbles for example):
- Look at Ice cores (such as Vostok in Antarctica, Greenland, as well as tropical mountain glaciers)
- Look at Geological rock sediments and isotopes (oxygen and silicon isotope fractionation in deep sea sediment/rock core samples for example)
- Ancient evidence can also be found in tree rings, ocean and lake sediments, coral reefs, layers of sedimentary rocks, stomata observed on fossil plant leaves, and reconstructed proteins from Precambrian organisms.
The last century and particularly in the last decade or few decades:
- Earth orbiting satellites, sensors and instruments flown by NASA (allows measurements on a global level)
- Ocean buoys
- Rain gauges
- The Moana Loa Observatory is a main centre for measuring climate change indicators
- Today’s scientists use sophisticated instruments and satellites to measure climate parameters. We can also look back through time by studying ice cores and sediment cores that provide indirect evidence about past temperatures and other climate conditions. Climate change is measured both globally and regionally.
- The most common climate observations are of temperature and precipitation. Other climate variables include humidity, wind speed and direction, air pressure, cloud cover and solar radiation.
- In polar regions, observed changes in sea ice, snow cover and glaciers also tell us what is happening with the climate.
- The most direct method for measuring atmospheric carbon dioxide concentrations for periods before instrumental sampling is to measure bubbles of air (fluid or gas inclusions) trapped in the Antarctic or Greenland ice sheets.
- Evidence for past temperatures comes mainly from isotopic considerations from sediment cores (up to 5 million years of data on climate change). This has proved crucial in studies on glacial/interglacial temperature.
- [climate variables started being measured in the mid 19th century, and by about 1970, earth orbiting satellites and more advanced technology was used]
- By carefully analysing the data gathered using these techniques (with careful account for changes in instrument types, observational practices, instrument locations and urban areas) it has been possible to map the distribution of temperature and other climate changes since the late 19th century.
- To study climate changes that occurred before direct measurements were made, scientists use indirect evidence from other sources that record a climate signal.
- These include climate signals encoded in the composition of ice cores, corals, sediments in oceans and lakes, and tree rings. All these records are laid down sequentially over time as an organism grows or as sediments accumulate.
- Ice cores from polar ice sheets, which are built from snow laid down over tens to hundreds of thousands of years, provide records of both past CO2 and temperature. As the snow transforms into ice, it traps air in sealed bubbles that provide a sample of past atmospheric composition, while the ratio of stable isotopes of either oxygen or hydrogen in the water molecule is related to the temperature at the time when the snow fell.
- More recent historical changes can be identified by analysing written and pictorial records, for example of changes in glacier extent.
Depending on how far back in time we are going, Wikipedia outlines what sort of data we analyse to get an idea of climate at that time – read more at https://en.wikipedia.org/wiki/Global_temperature_record
Climate Indicators/Factors That Might Be Measured
- Temperature – a primary indicator. Measured from earth’s surface, or sea surface temp. Can also measure air temperature. Can be measured with a thermometer or sensor.
- Precipitation – offers another indicator of relative climate variation, and may include humidity or water balance, and water quality. Covers rain, hail, snow, rime, hoar frost and fog, and is traditionally measured using various types of rain gages such as the non-recording cylindrical container type or the recording weighing type, float type and tipping-bucket type.
- Biomass & Vegetation Patters – may be discerned in a variety of ways and provide evidence of how ecosystems change to adapt to climate change. Refers to living and recently dead biological material and excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. It is usually measured by dry weight, and is the total mass of living matter. Can be measured via soil monitoring, insects and satellites.
- Sea Level – measurements reflect changes in shoreline and usually relate to the degree of ice coverage in high latitudes and elevations.
- Solar Activity – energy from the sun is measured both on the ground, and diffuse energy in the atmosphere. Different ‘meter’ measuring tools are used to measure the amount of solar energy and radiation or irradiance coming from the sun.
- Volcanic Eruptions – aerosol emitted is measured through instruments on satellites.
- Chemical – composition of air or water can be measured by tracking levels of greenhouse gases such as carbon dioxide and methane. Rock sediments and ice cores can reveal greenhouse gas levels, and ships, buoys, and satellites can reveal levels of ocean carbon.
More On What Is Measured, How It’s Measured, & Impacts/Effects That Are Monitored
This is not a comprehensive list, but it’s some of the ways of measuring, and some of the things scientists pay attention to with climate change and global warming:
What Is Measured
- Surface temperature
- Ocean temperature
- Sea levels
- Greenhouse gas quantities in the air (Mega and Giga tonnes). Particularly carbon dioxide, but also Methane, Nitrous Oxide and F Gases
- Greenhouse gas concentrations (in parts per million) in the air. Particularly carbon dioxide.
- Air bubbles in ice
- Energy arriving from the sun, and how much is leaving earth
- Wavelengths of greenhouse gases
- Amount of infrared trapped in earth’s atmosphere
How It’s Measured
- Satellite imagery, and other flying instrument technology
- Temperature and infrared gauges and devices
- Level gauges
- Ice cores
- Basic chemistry
- Basic Physics and advanced physics, such as spectroscopy for example
- Computer modelling (to compare non human influenced to human influenced climatic conditions to each other)
- Event Attribution
- Other physical, chemical, and electronic devices and data collection techniques
Impact And Effects Are Also Observed And Measured
- The impacts and effects of climate change and global warming on the environment and animals is also observed and measured to get an idea of how warming is occurring – such as glacial shrinkage and retreat for example
Other Notes On Measuring Climate Change & Global Warming Factors
- We can measure surface temperature from land stations, ships, and satellites and through accurate thermometers
- Carbon dioxide concentration in parts per million – In the case of carbon dioxide, the average concentration measured at the Mauna Loa Observatory in Hawaii, and numerous other stations worldwide
- Through chemistry, scientists know that when carbon based material is burned, it emits carbon dioxide (for example, coal is made mostly of carbon)
- We know roughly how much carbon based material we are burning
- We measure and know roughly how many tonnes of emissions we are producing – of carbon dioxide, methane, nitrous oxide and other GHGs
- Specifically we measure C02 since the Industrial revolution
- C02 can be measured from the C02 in the atmosphere, and the C02 trapped in ice
- Scientists can use satellites to measure the effect of CO2 to compare how much energy is arriving from the sun, and how much is leaving the Earth
- 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.
- 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.
- 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.
- By drilling or coring into ice, scientists can examine the bubbles of air trapped in ice cores
- Atmospheric C02 shows that increases are coming from burning fossil fuels
- Through physics, scientists know that C02 absorbs heat
- 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
- Through monitoring climatic conditions, we know recent warming of the Earth is correlated to and follows rising CO2 emissions
- Natural factors like the sun and ocean cycles that can influence climate have been ruled out
- Computer models can run experiments of natural versus human-influenced simulations of Earth
- Based on all this, there has been a consensus on climate change – specifically, humans are the root cause and also of the impact of climate change and global warming
- Event attribution studies for extreme weather have shown that rising temperatures doubled the risk of the torrential rains behind the Louisiana floods last August and that climate change was responsible for 70% of heat-related deaths in Paris during the 2003 heatwave.
- Climate models help us to understand the causes of past climate changes, and to project climate change into the future. Together with physical principles and knowledge of past variations, models provide compelling evidence that recent changes are due to increased greenhouse gas concentrations in the atmosphere
How Climate Change & Global Warming Is Observed
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 https://climate.nasa.gov/effects/
(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 that climate change and global warming experts might look out for, observe and monitor might be:
- 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
Having said that – there is uncertainty involved in predicting climate change into the future because of various factors which can change or can’t accurately be estimated. Future climates may be warmer or cooler than predictions. This is admitted by scientist – predictions are done with the best data and climate prediction models available – they aren’t guarantees.
A good description of how climate change is observed can be found at:
They talk about how average surface warming has slowed but global average temperature has increased, changes evident in the climate system, and how global climate change can be different to regional climate change in places like Australia.
4. Hannah Ritchie and Max Roser (2018) – “CO₂ and other Greenhouse Gas Emissions”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions’ [Online Resource]