Global Warming: It’s Later Than We Think…But It’s Not Too Late

Anthony J. BroccoliDirector, Center for Environmental Prediction

Department of Environmental SciencesRutgers University

Pulse of the Planet Lecture SeriesLiberty Science Center, Jersey City, NJ

January 26, 2008

Temperatures in the New York City area in the past 30 days have been:

a) more than 2°F below normalb) within 1°F of normalc) about 3°F above normald) more than 6°F above normal

Temperatures in the New York City area in the past 30 days have been:

a) more than 2°F below normalb) within 1°F of normalc) about 3°F above normald) more than 6°F above normal

Source: NOAA Climate Prediction Center

Source: NOAA Climate Prediction Center

“The balance of evidence suggestsa discernible human influence on global climate.”

Climate Change 1995 – The Second Assessment of the Intergovernmental Panel on Climate Change (IPCC)

“Most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas

concentrations.”

Climate Change 2000 – The Third Assessment Report of the IPCC

“The unequivocal detection of the enhanced greenhouse effectfrom observations is not likely for a decade or more.”

Climate Change – The IPCC Scientific Assessment (1990)

“Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to

the observed increase in anthropogenic greenhouse gas concentrations.”

Climate Change 2007 – The Fourth Assessment Report of the IPCC

The IPCC’s conclusion that the observed warming is very likely due to increasing greenhouse gases an that further warming is on the way is based on:

a) laboratory measurementsb) results from computer modelsc) climate observations d) all of the above

The IPCC’s conclusion that the observed warming is very likely due to increasing greenhouse gases an that further warming is on the way is based on:

a) laboratory measurementsb) results from computer modelsc) climate observations d) all of the above

What Are Climate Models?

Blue: Natural Pink: Natural + Human-induced

“It is extremely unlikely that global climate change of the past fifty years can be explained without external forcing.”

Variations among colored lines represents uncertainty due to uncertainty in future emissions.

Projections of Future Climate

Source: NOAA Geophysical Fluid Dynamics Laboratory

Simulating Future Climate ChangeSimulating Future Climate Change

Potential Climate Change ImpactsPotential Climate Change Impacts

Global Impacts of Climate ChangeGlobal Impacts of Climate Change

• There will be some winners, but more losers

• Densely populated coastal regions will face increased pressures from sea level rise and more extreme weather

• Poor communities and stressed ecosystems will suffer most, as they are already living “on the edge”

• 60% of world’s species are already responding to change

Report by IPCC Working Group II on Report by IPCC Working Group II on Impacts, Adaptation and Impacts, Adaptation and VulnerabilityVulnerability was released on 6 April 2007. Some of the was released on 6 April 2007. Some of the highlights from this report:highlights from this report:

Global Impacts of Climate ChangeGlobal Impacts of Climate Change

• There will be some winners, but more losers

• Densely populated coastal regions will face increased pressures from sea level rise and more extreme weather

• Poor communities and stressed ecosystems will suffer most, as they are already living “on the edge”

• 60% of world’s species are already responding to change

Report by IPCC Working Group II on Report by IPCC Working Group II on Impacts, Adaptation and Impacts, Adaptation and VulnerabilityVulnerability was released on 6 April 2007. Some of the was released on 6 April 2007. Some of the highlights from this report:highlights from this report:

Sea Level Trends in New Jersey

Source: National Oceanic and Atmospheric Administration

Atlantic City, NJ

NJ sea level rise= global sea level rise + other effects 0.4 m/century = 0.16 m/century + 0.24 m/century

Why is global sea level rising?

a) the density of the ocean is decreasingb) sea ice is melting rapidlyc) mountain glaciers are meltingd) the Greenland and Antarctic ice sheets are melting

Why is global sea level rising?

a) the density of the ocean is decreasingb) sea ice is melting rapidlyc) mountain glaciers are meltingd) the Greenland and Antarctic ice sheets are melting

Why Is Global Sea Level Rising?

• Thermal expansionWarmer water is less dense than colder water.

• Melting of glaciers and ice capsWater released by the melting of ice on land adds to the volume of the oceans.

• Melting and calving of Greenland and Antarctic ice sheetsDepends on the ice sheet dynamics (how the ice flows).

Why Is Global Sea Level Rising?

• Thermal expansionWarmer water is less dense than colder water.

• Melting of glaciers and ice capsWater released by the melting of ice on land adds to the volume of the oceans.

• Melting and calving of Greenland and Antarctic ice sheetsDepends on the ice sheet dynamics (how the ice flows).

Why Is Global Sea Level Rising?

• Thermal expansionWarmer water is less dense than colder water.

• Melting of glaciers and ice capsWater released by the melting of ice on land adds to the volume of the oceans.

• Melting and calving of Greenland and Antarctic ice sheetsDepends on ice sheet dynamics (how the ice flows).

Effects of Sea Level Rise on the Coastal Environment

Source: M. D. Beevers, U.S. Climate Change Science Program Workshop, Nov. 2005

Land area susceptible to inundation

Land area susceptible to coastal flooding (“30-yr flood”)

0.61 m (2 ft) sea level rise by 2100—middle of the road estimate.

1.22 m (4 ft) sea level rise by 2100—more melting from Greenland/Antarctica

“Ash Wednesday Storm”

Harvey Cedars, March 1962

New Brunswick, April 16, 2007John Munson/The Star-Ledger

Flood Stage

3 of 7 largest floodssince 2004

Warmer↓

MoreEvaporation

Warmer↓

MorePrecipitation

New Brunswick, April 16, 2007John Munson/The Star-Ledger

“…there is an increased chance of intense precipitation and flooding due to the greater water-holding capacity of a warmer atmosphere. This has already been observed and is projected to continue because in a warmer world, precipitation is concentrated into more intense events…” IPCC Fourth Assessment, 2007

IPCC: “It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent.”

day

s p

er y

ear

ove

r 90

ºF

day

s p

er y

ear

ove

r 10

0ºF

Changes in number of days with heat waves

from UCS Northeast Climate Impacts Assessment

Future Emissions ScenariosFuture Emissions Scenarios

All scenarios showincreasing emissionsduring next severaldecades

Some scenarios showdecreased emissionsin latter half of 21st

century

Even with aggressivereductions in emissions,CO2 would rise to 2xpreindustrial levels

More Warming in the Pipeline

Warming to date

Additional “zero-emission” warming (aka “commitment”)

Future emissions

Psychological Barriers?

• Climate change is not the result of malevolence.• Climate change does not violate our moral

sensibilities (i.e., cultural taboos).• Climate change is perceived as a future rather than

an immediate threat.• Climate change proceeds gradually.

Source: Daniel Gilbert, Harvard University, Los Angeles Times, July 2006

What actions would you favor for reducing the threat of climate change?

a) increase energy efficiencyb) capture and sequester CO2 from fossil

fuel burningc) increase nuclear power generationd) build more wind turbines and solar power systems

What actions would you favor for reducing the threat of climate change?

a) increase energy efficiencyb) capture and sequester CO2 from fossil

fuel burningc) increase nuclear power generationd) build more wind turbines and solar power systems

20562006

14

7

Billion of Tons of Carbon Emitted per Year

1956

0

Currently

projected path

Flat path

Historical emissions

1.9

2106

14 GtC/y

7 GtC/y

Seven “wedges”

““Wedges”Wedges”

O

Source: S. Pacala and R. Socolow, Princeton Univ.

15 Different Technologies Already in the 15 Different Technologies Already in the Marketplace at Industrial ScaleMarketplace at Industrial Scale

Coal to Gas

CCS

Nuclear

Renewables

Natural Sinks

Efficiency

The Global Warming Dilemma(J. Mahlman, In Solutions for an Environment in Peril, 2002)

“There are no quick policy fixes, nationally or globally. If we don't begin to chip away at the problem soon, it is very likely that serious consequences will be wired in for the world of our great-grandchildren and for their great-grandchildren....

The long time scales and robustness of the problem almost guarantees that our descendants in the 22nd century will, with historical perspective, see that we were actually confronted with a major planet-scale stewardship/ management problem.

They will most assuredly note how we responded, or how we did not respond to the problem.”

The climate is changing…

Why Is Global Sea Level Rising?

Melting Glaciers and Ice Caps:

Water released by the melting of ice on land adds to the volume of the oceans.

Global Warming and the Hydrologic Cycle

• The downward flux of radiative energy (i.e., sunlight and infrared radiation) at the surface is balanced by evaporation and sensible heating of the atmosphere.

• If the downward flux of energy increases, then evaporation will increase.

• On a global basis, evaporation and precipitation must balance.

• Thus as the earth warms, both evaporation and precipitation will increase.

Warmer↓

MoreEvaporation

Warmer↓

MorePrecipitation

LikelyMore likely than notLikelyIncreased incidence of extreme high sea level (excludes tsunamis)

Likely More likely than not Likely in some

regions since 1970 Intense tropical cyclone activity increases

Likely More likely than not Likely in many

regions since 1970s Area affected by droughts increases

Very likely More likely than not Likely

Heavy precipitation events. Frequency (or proportion of total rainfall from heavy falls) increases over most areas

Very likely More likely than not Likely Warm spells / heat waves. Frequency increases over most land areas

Virtually certain Likely (nights) Very likely

Warmer and more frequent hot days and nights over most land areas

Virtually certainLikelyVery likely

Warmer and fewer cold days and nights over most land areas

Likelihood of future trends based on

projections for 21st century using SRES

scenarios

Likelihood of a human contribution to observed trend

Likelihood that trend occurred in late 20th century

(typically post 1960)

Phenomenon and direction of trend

Detection Attribution Projection

Rahmstorf, Stefan, et al., 2007: Recent climate observations compared to projections. Science.Published online 2 February 2007, 10.1126/science.1136843

Dashed lines and gray shading are 2001 TAR projections. Colored lines are observations. While CO2 is increasing as projected, temperature is increasing a little more than all the scenarios.

“Sea level closely follows the upper gray dashed line, the upper limit referred to by IPCC as ‘including land-ice uncertainty.’ Note that the rate of rise for the last 20 years of the reconstructed sea level is 25% faster than the rate of rise in any 20 year period in the preceding 115 years.”

Global mean sea level changes

Changes in Heat Index

• The heat index combines the effects of temperature and humidity to estimate human comfort.

• Results are from simulations with three global climate models with two emissions scenarios, representing the low and high ends of the IPCC range.

• Under the high emissions scenario, Tri-State summers at the end of the 21st century are projected to be similar to those in Savannah, Georgia today.

Stippled areas are where more than 90% of the models agree in the sign of the change.

Relative changes in precipitation (%) for the period 2090–2099, relative to 1980–1999.

Simulated Changes in Precipitation

Increased frequency of heavy precipitation events over most areas: Very likely

More areas affected by drought: Likely