Projection of Global Climate Change

Review of last lecture Rapid increase of greenhouse gases (CO 2, CH 4, N 2 O) since 1750: far exceed pre-industrial values determined from ice core measurements spanning the last 650,000 years. Lead to strong radiative heating. Mainly caused by CO 2 fossil fuel use. The developed countries and developing countries contribute almost equally to the emissions of GHGs. Observed change of mean: air temperature, ocean temperature, melting of arctic sea ice, Greenland ice sheet, snow and glaciers, rising of sea level. Observed change of extreme events: extreme precipitation events, heat waves, strongest hurricanes

The most common atmospheric circulation structure L H H L Heating Cooling or No Heating Imbalance of heating  Imbalance of temperature  Imbalance of pressure  Wind Radiation Convection Conduction Latent/Sensible Biosphere Land/Ocean/Ice/Stra tosphere Feedback Greenhouse Gases Pollution Clouds Precipitation (Latent heat)

Coupler. Land Sea Ice Atmosphere Ocean Framework of Earth System Model Biogeochemistry Include 5 components: atmosphere, ocean, land, sea ice, biogeochemistry Based on the conservation laws of mass, energy, momentum, water vapor and other chemical species (e.g. CO 2, CH 4 ) Based on future assumptions of external forcing (GHG concentrations, solar variability, pollution, land use changes)

Can the GCMs Reproduce the 20th Century Temperature Trend? The GCMs can reproduce the 20th century temperature trend The warming is caused by anthropogenic forcings!

Simulations for Different Regions: Warming is caused by anthropogenic forcings

Our choice of the future: Emission scenarios

Projected Change in Global Mean Temperature

Global map of projected change Temperature: Largest warming over Arctic, larger over land Precipitation: Increase in tropics/poles, decrease in mid-latitudes

Video: Six Degrees Could Change the World (Carbon footprint 20:00-)

Number of Days over 100 o F

Vertical Structure of Projected Warming (Averaged over each latitude) Atmosphere: Tropical amplification (Glaciers, disease, …) Polar amplification (Ice, sea level) Ocean: Large warming goes down to ~1000 m (ecosystems)

Projected change of sea ice and ocean

Projected Change in Global Sea Level

Other examples: Nile Delta – 1m rise affects 6,000,000 people Florida, Louisiana - population centers, wetlands, tourism 1.5m rise expected 150 years from now (United Nations Environmental Program)

New York City under a 3-5m sea level rise

Projected Change in Precipitation: Increase in tropics and high latitudes, decrease in mid-latitudes

Impacts on fresh water

Impacts on ecosystems 4.0 o C 3.0 o C Poison ivy loves CO 2

Attribution of Projected Temperature Change: Mainly caused by anthropogenic forcings

Summary Global climate models: Earth system models (5 components) Global climate models can reproduce the observed warming in the 20th century. The warming is largely caused by human activities. Projected change: mean temperature (largest warming over Arctic, larger over land), mean precipitation, sea level, extreme temperature, extreme precipitation, fresh water, ecosystems Future climate scenarios show that reducing greenhouse gas emissions can substantially mitigate warming in the latter half of this century.

Work cited sentiment-remains-strong/ sentiment-remains-strong/ _011847http:// 2_ generating-industries/Post-Combustion-Carbon-Capture.aspxhttp:// generating-industries/Post-Combustion-Carbon-Capture.aspx pdfhttp://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE pdf/$file/EE pdf close-to-climate-tipping-point/ close-to-climate-tipping-point/