The Science of Global Warming

Andy BuddingtonSCC Earth Sciences Instructor

GLOBAL WHAT?SCC Sasquatch Times, 2008

March, 2008• Warmest on record for global land surface

temperature for month of March

• 2nd warmest on record for whole Earth (land & oceans)

• National Climatic Data Center, April 18, 2008

The Science of GWKey Points

• Greenhouse effect is real & essential• Natural climate variability & geologic time• Earth’s temp’s are indisputably warming• Anthropogenic GHG’s increasing• Observed & predicted effects of GW

Greenhouse EffectGreenhouse Effect process by which

certain atmospheric gases trap heat thus warming and insulating the planet.

Natural Greenhouse Gases • water vapor, carbon dioxide, methane,

ozone

Greenhouse Effect & GHG’s• Essential in maintaining Earth’s “livable”

temperature

• “natural” GHG’s maintain ~59oF global temperature

• Without natural GHG’s, ~3oF temperature

• However……..

Anthropogenic GHG’s & Effects

Climate Variability through Geologic Time

Long Term vs. Short Term Climate Cycles• Long Term 10’s of millions of years

• Short Term 10-100’s thousands of years

Causes?• Long Term plate tectonics

• Short Term orbital variations of planet

Earth’s Long-Term Climate Changes: Global “Ice Ages” (orange) vs. “Warm” episodes (blue)

Pleistocene: Short-Term Variations

• Abundant evidence of major warm-cold fluctuations throughout the Pleistocene

• Glacial advances vs. retreats• Minimum of 4 major advances (likely

many more) till deposits, moraines, etc• Driven by orbital variations (Milankovitch

cycles)

Pleistocene Ice Age 1.8 m.y. – ~12,000 b.p.

North America during the

Pleistocene

Ice Cores & Atmospheric Changes

• Antarctica & Greenland cores record greenhouse gas concentrations

• CO2, CH4, atmospheric dust, etc.

• Ice core data correlate with geologic data

Ice Core Data: Last 650,000 years

Antarctic Ice Core Data (Dome Concordia)

Note ~100,000 cycle peaks of CO2 & CH4

Last 40,000 years, Modern Climate

Note fluctuations from warm to cool but with overall warming

Really Modern!

So, What Do We Know About The Present Climate Change

Pattern?

Eight Warmest Years Worldwide(since the 1890’s)

#1 2005#2 1998#3 2002#4 2003

#5 2006#6 2004#7 2001#8 1997

11 of the 12 warmest years have occurred since 1995!20 of 21 warmest years have occurred since 1980!!

(National Climatic Data Center, 2006)

January-September 2007 land temperature warmest on record!

(National Climatic Data Center/October 16, 2007)

For January-September, 2007, year to date:• the global land surface temperature ranked

warmest on record • the Northern hemisphere land and land + ocean

surface temperature ranked warmest on record• the combined global land + ocean surface

temperature ranked fourth warmest on record

“Global What?” (SCC Sasquatch Times)

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”

IPCC, 2007

Present Temperature Trends• Earth’s climate is changing! warming• Are the present temperature trends

drastically different than geologic past?• YES! (unless Rush is right or you believe

the Sasquatch Times)

Projected Temps. @ present rates

What is Causing Present Temperature Trends?

• What is forcing (driving) present day climate change global warming?

• Natural or anthropogenic? • Role of Green House Gases critical

water vapor, CO2, CH4, N2O, CFC’s

Keeling Curve of Atmospheric CO2

• CO2 is about 30% higher• CO2 rate of increase, 200 x faster than at any time in

650,000 years EPICA project leader Thomas Stocker, University of Bern

Changing GHG Levels in Atmosphere

GHG 1750 levels Present Increase

CO2 280 ppm 384 ppm29%*

CH4 0.70 ppm 1.70 ppm143%

N20 280 ppb 360 ppb 11%

* CO2 increase 200x faster than anytime in last 800,000 years!!!

CO2 rises exceed worst-case scenarios(Proceedings of the National Academy of Sciences/May 22, 2007)

• The world's recent carbon dioxide emissions are growing more rapidly than even the worst-case climate scenario used by the Intergovernmental Panel on Climate Change (IPCC)

• C02 emissions from fossil fuels increasing at 3 times the rate of the 1990’s

CDIAC & EIA data compared to IPCC

Global mean surface temperature anomalies & simulations with natural forcings only

(IPCC AR4, 2007/ The Physical Science Basis/p. 684, Fig. 9.5)

Global mean surface temperature observations in black(anomalies relative to period 1901-1950)

AOGCM simulation range in blue/mean in dark blue (58 simulations/14 models)

Global mean surface temperature anomalies & simulations with anthropogenic forcings

(IPCC AR4, 2007/ The Physical Science Basis/p. 684, Fig. 9.5)

Global mean surface temperature observations in black(anomalies relative to period 1901-1950)

AOGCM simulation range in yellow/mean in red (58 simulations/14 models)

Measured & Anticipated Impacts

• Impacts on the atmosphere• Impacts on the hydrosphere• Impacts on the cryosphere• Impacts on the geosphere• Impacts on the biosphere• Impacts on the anthroposphere

Global warming impacts on the atmosphere

• Increasing air temperatures • Migration of climate zones• More extreme weather events

• heat waves & droughts• intensified storms & floods

Global warming impacts on the hydrosphere

• Impacts on sea surface temperatures • Impacts on ocean acidity (pH)• Impacts on sea level• Impacts on ocean circulation• Impacts on tropical storms• Impacts on rainfall and floods• Impacts on lakes

Projected Sea Level RiseTwo main contributing factors • Warming ocean water expands, causing

increased sea levels

• Melting glaciers will deliver water to oceans

• Present rate ~1inch/decade

Projected Sea Level Rise

• Greenland ice sheet ~23’ rise in SL• West Antarctic ice sheet ~16’ rise• East Antarctic ice sheet ~190’ rise

Projected Sea Level Rise

Ocean acidity studies: ocean acidity (pH level) is changing

• ocean pH stable from 1000 to 1800 years• drop of 0.1 of a pH unit from 8.16 to 8.05

(since the industrial revolution)• Predicted 0.3-0.4 drop by 2100

RESULT reduced carbonate uptake by CaCO3 secreting organisms plankton, coral, etc.

Global warming impacts on the cryosphere

• Impacts on Arctic sea ice• Impacts on Greenland• Impacts on permafrost & tundra• Impacts on Antarctica• Impacts on mountain glaciers

September Arctic sea ice at record low(NASA/Earth Observatory/September 16, 2007)

Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 (23% less) and substantially below the long-term average

Greenland melt zone 1979-2002(Arctic Climate Impact Assessment, 2004)

*Greenland has warmed 7.2oF since 1991

NASA GRACE satellite detects significant Antarctic ice mass loss

(University of Colorado/March 2, 2006)

(photo courtesy British Antarctic Survey)Isabella Velicogna and John Wahr of the University of Colorado (Boulder) demonstrated for the first time that Antarctica's ice sheet lost a significant amount of mass since the launch of GRACE [Gravity Recovery and Climate Experiment] in 2002.

RELEASE: 06-085

Global warming impacts on permafrost & tundraWestern Siberia thawing for the first time in 11,000 years

(New Scientist/August 11, 2005)

• An area stretching for a million square kilometers across the permafrost of western Siberia is turning into a mass of shallow lakes as the ground melts.

• The sudden melting of a bog the size of France and Germany could unleash billions of tons of methane, a potent greenhouse gas.

• Sergei Kirpotin of Tomsk State University describes an "ecological landslide that is probably irreversible and is undoubtedly connected to climatic warming.“

• Western Siberia has warmed some 3 °C in the last 40 years. (photo courtesy of BBC News)

Permafrost Carbon• Researchers estimate ~1000 gigatons of

carbon in world’s permafrost

• Humanity 6.5 gigatons/year• Permafrost carbon methane (CH4)

• CH4 21 times more “powerful” GHG!

Melting sea ice stresses polar bears(Integrative and Comparative Biology/April, 2004)

(photo by Dan Crosbie)

• Polar bears cannot survive without sea ice and, in all likelihood, summer sea ice will be gone from the north polar basin within the next few decades (Center for Biological Diversity 6/15/06)

• Given the rapid pace of ecological change in the Arctic, the long generation time and highly specialized nature of polar bears, it is unlikely that polar bears will survive as a species if the sea ice disappears

Other Measured Effects

Global warming impacts on the anthroposphere

• Impacts on communities and ecosystems

• Impacts on water and agriculture• Impacts on disease and health

Is Today’s Global Warming Different?Is Today’s Warming Trend Any More

Significant Than The Past?Is Today’s Warming Serious?

“We have a very brief window of opportunity”

Dr. James Hansen, Director, NASA Goddard Institute for Space Studies

“We have a very brief window of opportunity to deal with climate change . . . no longer than a decade at the most.“

If the world continues with "business as usual," temperatures will rise by 2 to 3o Celsius (3.6 to 7.2o F) and "we will be producing a different planet"

Senator James Inhofe, R-Oklahoma

Senate Committee on the Environment and Public Works

"much of the debate over global warming is predicated on fear, rather than science." I called the threat of catastrophic global warming the "greatest hoax ever perpetrated on the American people,"

“most media-hyped environmental issue of all time”

“the American people have been served up an unprecedented parade of environmental alarmism by the media and entertainment industry”

What if the scientists are wrong about global warming?

I left Earth three times, and found no other place to go. Please take care

of Spaceship Earth.Wally Schirra, NASA

IT IS TIME TO ACT!

(AP photo courtesy of Dan Crosbie/Canadian Ice Service)