Global Warming Political hype or reality The Fernhurst

Global Warming ‘Political hype or reality? ’ The Fernhurst Society - 5 April 2007 John Clement

Global warming - questions u What is happening? u What are the reasons? u What is likely to happen from now on? u What can we do?

What’s happening? Observable warming Trending strongly above long-term averages since mid ‘ 70 -s

NOT the Earth’s long-term climate cycle +50 -5‘ 000 years before present This cycle is driven by Earth’s orbit changes

What’s happening? Consistent observations Similar trending since mid ‘ 70 -s by three independent measures

What are the reasons? The climate system

What are the reasons? Radiation balance u Energy coming into the Earth from the Sun — SOLAR radiation u Energy leaving the Earth to outer Space — INVISIBLE INFRARED radiation

Solar radiation at poles and equator Near the poles, the Sun’s rays are spread out over a wide area, so the heating is less intense SUN’S RAYS Near the equator, the Sun’s rays are spread out over a smaller area, so the heating is more intense The Earth’s climate systems in the atmosphere and oceans transport heat between the equator and the poles - and produce the ‘weather’

Range of global temperatures

What are the reasons? Is it solar radiation?

What are the reasons? Solar radiation? 0. 1 0 Implied changes in global temperature (°C) 0. 2 Solar radiation – has been stable for the last 50 years

What is the reason? u Energy coming into the Earth from the Sun — SOLAR radiation u Energy leaving the Earth to outer Space — INVISIBLE INFRARED radiation

What is the reason? The ‘greenhouse’ effect?

What is the reason? The ‘greenhouse’ effect?

Greenhouse gas increases through Industrial Age u CO 2 – roughly constant at 280 ppm until 1800 – then rising rapidly to 380+ ppm today, and further yet. u Methane – 800 ppb until 1800, now 1, 750 ppb. u Nitrous oxide 270 ppb until 1800 – now 310 ppb u Lower atmosphere ozone increased around 30% over the same period.

Greenhouse gases Predicted warming effect over the next 100 years Methane 24% Nitrous oxide 10% Carbon dioxide 63% Others 3% CO 2 is the major contributor

Volcanoes also affect the atmosphere

Volcanic aerosols in the atmosphere 1883 Krakatau 5 4 4 3 3 2 2 1 1 0 0 1980 Mt. St. Helens Estimated cooling effect, Wm 1991 Mt. Pinatubo 5

What’s happening? Observable warming Suspected effect of atmospheric particulates Trending strongly above long-term averages since mid ‘ 70 -s

Climate models - improving

Natural factors alone do not explain the pattern of global warming since industrialisation

CO 2 in the atmosphere – long term stability until industrialisation The Industrial Age

CO 2 from fossil fuels – rapid rise since 1950

Addition of man-made factors to models duplicates observations

Q. Global Warming? Change between 1750 and 2000 A. Man-made gases dominate

Global warming - questions u What is happening? u What are the reasons? u What is likely to happen from now on? u What can we do?

Global warming u What is happening? u What are the reasons? u What is likely to happen from now on? u What can we do?

What is likely to happen from now on? u Depends on what we do. u Slowing down GHG emissions, particularly carbon, will mitigate future temperature rises – but there is a lot of momentum already embedded in the climate system. u Adaptation will be needed for coming changes in – rainfall patterns - glaciers and sea-ice - sea-levels - land temperatures - food crop, forest and animal ranges - human impacts – livelihoods, wealth and health

Rainfall Glaciers and sea-ice Sea levels Land temperatures

Rainfall - changing

UK precipitation by 2080 s

European summer rainfall outlook - 2080 s

Rainfall Glaciers and sea-ice Sea levels Land temperatures

Glaciers – melting 16, 700 in the world – 13, 500 are in retreat

Gangotri glacier, Himalayas – a case study

Himalayan glaciers - critical

Himalayan glaciers - critical Himalayan glaciers feed 7 of Asia’s great rivers - The Ganges - The Indus - The Brahmaputra - The Salween - The Mekong - The Yangtze - The Yellow river 2. 3 billion people

Rainfall Glaciers and Sea-ice Sea levels Land temperatures

Sea ice – also melting 1. 3 million km 2 Arctic ice lost since mid-70 s

Arctic sea-ice, maybe disappearing by 2080 s

West Antarctic and Greenland ice sheets 1, 000 years to melt , but……. . = 6 m sea level rise = 7 m sea level rise

Oceans - The north Atlantic Conveyor

Hypothetical collapse in ocean currents

Best forecasts of Atlantic circulation – its OK!

Rainfall Glaciers and sea-ice Sea levels Land temperatures

Components of sea level rise

Long-term momentum of sea-level rises

IPCC estimates of global mean sea-level rise

North Sea storm surges by 2080

Rainfall Glaciers and sea-ice Sea levels Land temperatures

European hot summers – human activity has roughly doubled the chances

European summer temperatures rising 2003

Global warming - questions u What is happening? u What are the reasons? u What is likely to happen from now on? u What can we do?

What can we do? u Avoid unnecessary carbon u Be prudent with necessary carbon u Offset and seuester as much carbon as possible u Adapt

CO 2 concentration (ppm) CO 2 emissions reductions - the only route to stable concentrations. 750 Business as usual 650 Constant 1990 emissions 550 450 50% 1990 emissions 350 ◄ Pre-industrial concentration 250 1990 2010 2030 Year 2050 2070 2090

No getting away from it – future warming

What can we do? u Avoid unnecessary carbon u Be prudent with necessary carbon u Offset and sequester as much carbon as possible u Adapt Cross fingers for approx. 200 years!

The End The Fernhurst Society - 5 April 2007 A presentation by John Clement