Global Warming

Global WarmingGlobal Warming

Inez Fung

University of California, Berkeley

April 2007

Climate Change: Recent News

• Feb 7 2007: United Nations Env Programme - Intergovt Panel on Climate Change - observed warming since the 20thC is very likely due to anthropogenic greenhouse gases

• April 2 2007: US Supreme Court: anthropogenic CO2 is a pollutant

• April 7 2007: UNEP IPCC WG 2 - warming has had discernible influence on physical and biological systems

Changing Composition of the Atmosphere

Analysis of ancient air bubbles trapped in ice

Direct measurements of atm composition in the past centuries

Increases since 1800 due to human activities

At equilibrium:High CO2 --> warm; Low CO2 --> cold

J. Hansen

The Last 500,000 years

and

the last 200

years

J. Hansen

Global mean temperatures are rising faster with time

100 0.0740.018

50 0.1280.026

Warmest 12 years:1998,2005,2003,2002,2004,200

6, 2001,1997,1995,1999,1990,200

0

Period Rate

Years /decade

IPCC AR4

The most important spatial pattern (top) of the monthly Palmer Drought Severity Index (PDSI) for 1900 to 2002.

The time series (below) accounts for most of the trend in PDSI.

Drought is increasing most places

Mainly decrease in rain over land in tropics and

subtropics, but enhanced by increased atmospheric demand

with warming

IPCC AR4

Climate Feedbacks

Warming

Evaporation from ocean,Increase water vapor in atmEnhance greenhouse effect

Decrease snow cover;Decrease reflectivity of surfaceIncrease absorption of solar energy

Increase cloud cover;Decrease absorption of solar energy

AttributionAttribution

• are observed changes consistent with

expected responses to forcings

inconsistent with alternative explanations

Observations

Climate model: All forcing

Climate model: Solar+volcanic only

IPCC AR4

9oF

7oF

3oF

Projections of Climate Change

IPCC AR4

greatest over land & at most high N latitudes

and least over the South. Ocean & parts of the N Atlantic Ocean

Projections of Climate Change

IPCC AR4

Jay Zwally

Warming is faster than model projections: Recent rapid melting glaciers on Greenland

Stern Review 2006

Stern Review 2006

Strong action is needed urgentlyStrong action is needed urgently

Ste

rn R

evie

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