Climate ChangeWhat Does the Science Really Tell Us?

Craig CoggerWSU Puyallup

Simplified Greenhouse Effect

Solar energy passes through atmosphere and is absorbed by the earth

Energy radiates back toward space as lower-energy infrared waves

Greenhouse gases absorb and re-radiate some of the infrared energy, trapping heat in the atmosphere.

1

23

Greenhouse Gases

• CO2, H2O, N2O, CH4:Absorb infrared energyAct like a blanket

• Without the greenhouse effect, earth’s mean temperature would be 0o F, nearly 60o lower than it is now

Carbon Dioxide

Water

The Problem:We are increasing atmospheric CO2, adding to the greenhouse effect, and warming the planet

NASA

G. Holloway, Instituteof Ocean Sciences,

Sidney, BCUCAR USDOE PNNL

Ocean Circulation moves and stores heat and CO2

Atmospheric Circulation moves heat

Carbon Cycle moves, transforms, and stores CO2

Aerosols interact with solar energy

Some of the Complicating Details

Definitions:Weather and Climate

• Weather: The current state of the atmosphere (hours, days, weeks, months)

• Climate: Average weather over time (30 years or more)

• Climate is what you expect, weather is what you get

San Antonio DailySan Antonio Daily

Weather:

Climate:

http://data.giss.nasa.gov/gistemp/graphs/

Climate Forcing

• Climate forcing: Affects global energy balance, forcing a change in climate

• Examples:o Changes in solar energy

(sunspot cycles, orbital changes – small over short time scales)

o Changes in greenhouse gas concentrations (CO2, CH4, N2O, others)

o Aerosols

NOAA

Minnesota public radioUSGSUSGS

Climate FeedbackAmplifies or dampens climate forcing

• H2O in atmosphere: Positive feedback, increases warming

• Snow and ice melting: Positive feedback – more melting, less reflection of heat, more warming

• Melting permafrost and thawing soil releasing greenhouse gases: Positive feedback

• Changes in cloud cover: Both positive and negative

NASA

UNEP

Katey Walter, UAF

Jon Sullivan

http://data.giss.nasa.gov/gistemp/graphs/

Evidence for Current Climate Change:Temperature Anomalies

Evidence for Current Climate Change:Temperature Extremes – US 48 states

www.ucar.edu

Evidence for Current Climate Change:Sea Ice Extent

USGS

Evidence for Current Climate Change:Accelerating Glacier Loss

Evidence for Current Climate Change:Ecosystem Changes

• Bleached coral reefo Coral death and decline appear

linked to increased water temperatures

• Pine bark beetle damageo Extreme cold keeps beetle

populations in check. Recent severe infestations appear related to moderating winter temperatures

US Forest Service

NOAA

Evidence for Current Climate Change:Sea Level Rise

http://sealevel.colorado.edu/

Evidence for Current Climate Change:

http://www1.ncdc.noaa.gov/pub/data/cmb/bams-sotc/2009/bams-sotc-2009-brochure-lo-rez.pdf

IPCC 4th Assessment

IPCC Regional Temperature ProjectionsChange compared with 1980-1999 baseline

IPCC 4th Assessment

IPCC Regional Precipitation Projections for 2090-2099Compared with 1980-1999 baseline

Saiful Huq Omi/Polaris, for The New York Times

Land at risk from 1m sea level rise

Watts Up With That? Commentary on puzzling things in life, nature, science, weather, climate change, technology, and recent news by Anthony Watts

Isn’t there another point of view?

Not one with a credible scientific basis.

The Global Challenge

• 86% of world’s energy comes from fossil fuel• Deforestation is #2 human source of CO2

• Target 80% reduction in CO2 emissions by 2050 to avoid worst outcomes of climate change

• Individual and government action needed

Responding to the climate change challenge

We basically have three choices: mitigation, adaptation and suffering. We’re going to do some of each. The question is what the mix is going to be. The more mitigation we do, the less adaptation will be required and the less suffering there will be. John Holdren

The “Wedge Strategy” for Mitigation

• Each wedge plays a role in reducing greenhouse gas emissions

• Think of how our industry can contribute to these wedges.

NRDC

Getting Involved

• Reduce emissions at home and work

• Learn more about climate science

• Talk to your friends, neighbors, and co-workers

• Write to decision makers• Support organizations who

work for those in greatest need

Take-home message• Greenhouse effect

– Science is unassailable: Added greenhouse gases warm the earth

• Multiple lines of evidence show effects of warming across the globe

• We need to act now to avoid the most severe harm to people and the environment.

Looking to the future:Many of the youngest among us will still be alive in the closing decades of

this century. How can we shape the world will they be living in?

Recommended Reading

IPCC synthesis of the best science, 2007(already a little out-of-date)

Well written by a physicist/historian, 2008

Readable, robust science, 2009

Trustworthy climate science blogs