Climate Change: A Scientist’s Perspective

Taplin Lecture Princeton Environmental Institute

April 7, 2011

Ralph J. Cicerone, President

National Academy of Sciences

What is Happening?

Is There an Explanation?

Is There An Alternate Explanation?

What Can Be Predicted?

Science and Climate Change

Earth’s Energy Balance 

The Greenhouse Effect 

Observed Changes 

Temperatures of Air and Water 

Sea-Level Rise 

Ice Losses from Greenland & Antarctica 

Future Fossil-Fuel Usage

OUTLINE

Over Earth’s history, climate has changed many times

(global sea level, ice amounts, windiness, rain amounts).  What forces control or influence climate?  How can humans affect our planet’s climate?

239

102

341

68

169

390

327 90

16

H2O, CO2, O3

Earth receives visible light from hot Sun and Earth radiates to space as a

blackbody at infrared wavelengths

Calculating the Surface Temperatures of Planets

for Venus

Actual Te = 450 ºC Greenhouse effect and clouds, high pressure

S(1 - e

for Earth, S = 341 W/m2, = 0.3, so we calculate

Te = - 18 ºC (or - 32 ºF)

Greenhouse effect & clouds are needed

WRONG !

WRONG !

for Mars

Te = - 28 ºC (± 5 ºC) (large day/night swings)

Greenhouse effect is very small, low pressure

OK !

Infrared

Visible

[Hanel et al. (1972)]

Energy in the Climate System

Averaged over the whole Earth

All Human Energy Usage 0.025 watts/meter2

Extra Heat Trapped by Greenhouse gases (2007) 2.6 watts/meter2

Energy Absorbed from Sunlight 239 watts/meter2

www.scrippsco2.ucsd.edu

http://agage.eas.gatech.edu

[Hansen and Sato (2004)]

CO2 Increase is from Human Activities:

Approximate Fractions

• 85% from fossil fuels

• 15% from deforestation

http://data.giss.nasa.gov/gistemp/graphs12 Jan 2011

http://data.giss.nasa.gov/gistemp/graphs12 Jan 2011

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

Levitus et. al. (2009)

Time series of yearly ocean heat content (1022J) for the 0–700 m layer from this study (solid) and from Levitus et al. [2005a] (dashed). Each yearly estimate is plotted at the midpoint of the year. Reference period is 1957–1990.

1882-2005 sea level rise based on Permanent Service for Mean Sea Level (PSMSL) tide gauge data from 23 sites selected by Douglas (1997)

This figure was prepared by Robert A. Rohdehttp://www.globalwarmingart.com/wiki/Image:Recent_Sea_Level_Rise.png

Rel

ativ

e S

ea L

evel

(cm

)

Source : University of Colorado, Boulder http://sealevel.colorado.edu

Greenland Mass Loss – From Gravity Satellite

Velicogna (2009 GRL), updated by Velicogna (2011)  

Trend Apr 2002-Sep 2010: -240±33 Gt/yr (= 0.7 mm/yr sea level rise)

ACCELERATION: -17 ±8 Gt/yr2

Greenland Ice mass loss from GRACE

Antarctica Ice mass loss from GRACE

Trend Apr 2002-Sep 2010: -143 Gt/yr (= 0.4 mm/yr sea level rise)

ACCELERATION: -17 Gt/yr2

Velicogna (2009 GRL), updated by Velicogna (2011)  

Global annual mean surface temperature anomalies, observed

and calculated.

From Stott et. al. (2006)

ALL

NATURAL

Physical Principles Explain the Warming Since the late 1970’s through the

Greenhouse Effect

http://data.giss.nasa.gov/gistemp/graphs12 Jan 2011

Solar irradiance through September 2008. Reference: Fröhlich, C. and J. Lean, Astron. Astrophys. Rev., 12, pp. 273--320, 2004. http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant

Boden & Marland (2009) cdiac.ornl.gov

0

10002000

3000

40005000

6000

70008000

900017

51

1767

1784

1800

1816

1832

1848

1864

1880

1896

1912

1928

1944

1960

1976

1992

2007

Total Emissions

Global Fossil-Fuel Carbon Dioxide Emissions, 1751 to 2007Includes Cement Manufacturing

All emissions estimates are expressed in million metric tons of carbon

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

World marketed energy consumption, 1990-2035(quadrillion Btu)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

Shares of world energy consumption in the United States, China, and India, 1990-2035 (percent of world total)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

Coal consumption in selected world regions, 1990-2035 (quadrillion Btu)

Pre-Industrial 280ppm

380ppm

425 ～ 440ppm

Present

Dangerous Level

Global Carbon Cycle Management

Anthropogenic Emission 7.2 GtC / y

Absorption3.1 GtC/ y

How to control the tap

to avoid risk

industrialization

CO2 in Atmosphere

Ocean 　 2.2 Land 　 0.9

2ppm/y

ex: 2.4-2.8 rise from PI℃

Feedback 　

Adapted from Nishioka, NIES, Japan

In future climate:

Global temperatures ?

Sea-level rise ?

Precipitation amounts in each region and season?

Frequencies of extreme events?

How to limit CO2 emissions from fossil-fuel burning?

Oceans acidifying as well as warmingpH history and “business as usual” projection

Red line is global annual average; blue lines show ocean-to-ocean and seasonal variation.

Surface ocean pH has already fallen by 0.1 pH unit. Projected additional changes are likely to have large impacts on corals and other ocean organisms that make skeletons/ shells from calcium carbonate.

Article 2, UN Framework Convention on Climate Change (1992)

“The Ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable in a sustainable manner.”

Who Should Define "Dangerous" ?

scientists?

elected leaders?

____________ ?

Clathrate Decomposition 5? Tg/yr (0.9%)

Termites40 Tg/yr (7.4%)

Freshwaters5 Tg/yr (0.9%)

Wetlands115 Tg/yr (21.3%)Boreal: 20 – 60 Tg/yr

Oceans10 Tg/yr (1.9%)

Rice Paddies110 Tg/yr (18.5%)

Biomass Burning55 Tg/yr (10.2%)

Landfills40 Tg/yr (7.4%)

Global Methane Release Rates

Coal Mining35 Tg/yr (6.5%)

Gas Production45 Tg/yr (8.3%) Enteric Fermentation

80 Tg/yr (14.8%)

Cicerone & Oremland, 1988Total = 540 Tg/yr

Immediate action with multiple benefits.

Energy efficiency would: decrease our dependency on foreign oil improve our national security decrease our trade deficit decrease local air pollution increase our national competitiveness encourage development of new products for

global markets decrease household energy costs while also

slowing the increases of CO2 and CH4 !

Evidence• Time history of CO2 increase and that of fossil-fuel usage

• Amounts of atmospheric CO2 increase

(0.6 x fossil-fuel emissions)

• Contemporary atmospheric amounts exceed those of

previous four glacial cycles

• Geographical patterns of atmospheric CO2

• Isotopic contents of CO2

• Ice-core data show that CH4 and N2O amounts are

also unprecedented

Extreme heat waves in Europe, already 2X more frequent because of global warming, will be “normal” in mid-range scenario by 2050

Black lines are observed

temps, smoothed &

unsmoothed; red, blue, &

green lines are Hadley Centre simulations w

natural & anthropogenic forcing; yellow is natural only.

Asterisk and inset show 2003 heat wave that killed 35,000.

Stott et al., Nature 432: 610-613 (2004)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

World electricity generation by fuel, 2007-2035 (trillion kilowatthours)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

Renewable electricity generation in China by energy source, 2007-2035 (billion kilowatthours)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

World liquids consumption by region and country group, 2007 and 2035 (million barrels per day)

EIA, International Energy Statistics database (as of November 2009), web site www.eia.gov/emeu/international. Projections: EIA, World Energy Projection System Plus (2010).

World liquids consumption by sector, 2007-2035 (million barrels per day)

The challenge of scale

• Stabilizing at 500 ppmv CO2-e means global CO2 emissions must be ~7 GtC/yr below BAU in 2050.

• Avoiding 1 GtC/yr requires… - energy use in buildings cut 20-25% below BAU in 2050, or

- fuel economy of 2 billion cars ~60 mpg instead of 30, or

- carbon capture & storage for 800 1-GWe coal-burning power plants, or

- 700 1-GWe nuclear plants replacing coal plants, or

- 1 million 2-MWe(peak) wind turbines replacing coal power plants or

- 2,000 1-GWe(peak) photovoltaic power plants replacing coal power plants

Socolow & Pacala, 2004