The Science of Climate ChangeWhy We Believe It and What Might Happen

Dave Stainforth,University of Exeter

Tyndall Centre for Climate Change Research

London School of Economics

Environmental Change Institute, Oxford University.

Climate Change – The BasicsAtmospheric Greenhouse Gas Levels are Increasing

Source: IPCC Fourth Assessment Report (SPM)

Climate Change – The BasicsScenarios of Future Human Activity

Note different scale! Source: IPCC Third Assessment Report

In 2005 CO2 concentrations were about 380ppm but greenhouse gas concentrations were about 430 ppme (ppm equivalent)

Climate Change – The BasicsGlobal Temperatures and Sea Levels are Rising

Source: IPCC Fourth Assessment Report (SPM)

Climate Change - FundamentalsCommitment to Further Warming

We are committed to further warming based on past emissions alone.Around 0.5°C - 1°C according to Wigley 2005 and Meehl, 2005.

Climate Change: Global Projections

By 2020s we can expect global temperatures to be between 0.3°C and 1.3°C warmer than the 1990s.(Stott and Kettleborough, 2002)

Figure SPM.5Source: IPCC Fourth Assessment Report (SPM)

"We need to treat climate change not as a long term threat to our environment, but as an immediate threat to our security and prosperity," John Ashton,

UK Climate Ambassador at the Foreign Office

2006

Terminology – Mitigation and Adaptation

Mitigation: “A human intervention to reduce the sources or enhance the sinks of greenhouse gases.”

Adaptation: “Adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploit beneficial opportunities”

Terminology – Mitigation and Adaptation

Mitigation Adaptation

What is Climate Science?

Maths: non-linear systems, chaos, game theory…

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What is Climate Science?

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Ideal gas law (equation of state of an “ideal” gas)

Physics: atmosphere, oceans, clouds …

What is Climate Science?

Maths, physics, statistics, hydrology, geomorphology, ecology, agricultural science, economics, political science, international development …

Climate change science is a new science. Climate change science is a mixture of many different

disciplines; getting them to work together is itself a challenge.

Climate Change: Why we believe it’s a significant global problem

Basic physics: Atmospheric GHGs increase

surface temperatures.(The earth would be 30oC colder if they didn’t.)

GHGs should increase surface temperatures.(Just based on their basic radiative properties.)

Observations: Global mean temperatures are

increasing.

Some Sceptic Arguments:news.bbc.co.uk/2/hi/science/nature/7081026.stm

1. Evidence that the earth's temperature is getting warmer is unclear.2. If the average temperature was rising, it has now stopped.3. The earth has been warmer in the recent past.4. Computer models are not reliable.5. The atmosphere is not behaving as models would predict.6. Climate is mainly influenced by the sun.7. A carbon dioxide rise has always come after a temperature

increase not before.8. Long-term data on hurricanes and arctic ice is too poor to assess

trends.9. Water vapour is the major greenhouse gas; co2 is relatively

unimportant.10.Problems such as hiv/aids and poverty are more pressing than

climate change.

Some Sceptic Arguments:news.bbc.co.uk/2/hi/science/nature/7081026.stm

1. Evidence that the earth's temperature is getting warmer is unclear.2. If the average temperature was rising, it has now stopped.3. The earth has been warmer in the recent past.4. Computer models are not reliable.5. The atmosphere is not behaving as models would predict.6. Climate is mainly influenced by the sun.7. A carbon dioxide rise has always come after a temperature

increase not before.8. Long-term data on hurricanes and arctic ice is too poor to assess

trends.9. Water vapour is the major greenhouse gas; co2 is relatively

unimportant.10.Problems such as hiv/aids and poverty are more pressing than

climate change.

Feedbacks

Feedbacks: water vapour, clouds, land surface, ice sheets, methane hydrates …

The sceptic view: Negative feedbacks in the climate system will counteract any potential warming due to increased atmospheric GHGs. (e.g. Richard Lindzen’s Iris effect)

What happens next.

Figure SPM.5

UK Climate Impacts Programme Scenarios

“The UKCIPnext climate change scenarios will be presented … as probability distributions.” They will be available for 25km grid boxes.“Model outputs will include changes in temperature, precipitation, snowfall, wind speed, humidity, cloud cover, solar radiation, air pressure and soil moisture content.”Source : UKCIPnext Consultation

Climateprediction.net, distributions and ranges

Mediterranean Basin Northern Europe

Winter Winter

Summer Summer

AnnualAnnual

Exploring Possibilities

Going Forward

We all need to start debating how to respond to climate change – not whether it is happening.

To get the best out of the science, industry and academia need to work together.

Climate change is happening, but is it man-made?The Royal Society has a website which answers this.