Greenhouse Gases and Climate Change:Global Changes and Local Impacts

Anthony J. BroccoliDirector, Center for Environmental Prediction

Department of Environmental SciencesRutgers University

New Jersey Clean Air CouncilApril 11, 2007

“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 temperaturessince 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

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

Red, green, and blue lines represent different emissions scenarios.

Height of each colored bar represents variations among different climate models.

Potential Climate Change ImpactsPotential Climate Change Impacts

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?

• 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).

Global mean sea level changes

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”)

50% probability of 0.61 m sea level rise by 21001% probability of 1.22 m sea level rise by 2100

Effects of Climate Change on Water Resources

Floods and Droughts?

Warmer↓

MoreEvaporation

Warmer↓

MorePrecipitation

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.

“Increases in the amount of precipitation are very likely in high-latitudes, while decreases are likely in most subtropical land regions, continuing observed patterns in recent trends.”

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

Flood Stage

More Climate Change in the Pipeline

Warming to date

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

Future emissions

Managing Climate Change

• Leadership: Raise public awareness of the challenges posed by climate change and the need to mitigate and adapt.

• Mitigation: Reduce emissions of carbon dioxide and other greenhouse gases.

• Adaptation: Increase the resilience of society to climate change.

• Knowledge: Develop a better understanding of the details of future climate change.