Global Warming: It’s Later Than We Think…But It’s Not Too Late Anthony J. Broccoli Director, Center for Environmental Prediction Department of Environmental Sciences Rutgers University Pulse of the Planet Lecture Series Liberty 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 normal b) within 1°F of normal c) about 3°F above normal d) more than 6°F above normal

Source: NOAA Climate Prediction Center

“The balance of evidence suggests a 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 effect from 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 measurements b) results from computer models c) 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 Change

Potential Climate Change Impacts

Global 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 Impacts, Adaptation and Vulnerability was released on 6 April Some of the highlights from this report:

Global 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 Impacts, Adaptation and Vulnerability was released on 6 April Some of the 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 m/century

Why is global sea level rising? a) the density of the ocean is decreasing b) sea ice is melting rapidly c) mountain glaciers are melting d) the Greenland and Antarctic ice sheets are melting

Why Is Global Sea Level Rising? Thermal expansion Warmer water is less dense than colder water. Melting of glaciers and ice caps Water released by the melting of ice on land adds to the volume of the oceans. Melting and calving of Greenland and Antarctic ice sheets Depends on the ice sheet dynamics (how the ice flows).

Why Is Global Sea Level Rising? Thermal expansion Warmer water is less dense than colder water. Melting of glaciers and ice caps Water released by the melting of ice on land adds to the volume of the oceans. Melting and calving of Greenland and Antarctic ice sheets Depends on the ice sheet dynamics (how the ice flows).

Why Is Global Sea Level Rising? Thermal expansion Warmer water is less dense than colder water. Melting of glaciers and ice caps Water released by the melting of ice on land adds to the volume of the oceans. Melting and calving of Greenland and Antarctic ice sheets Depends 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 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 m (4 ft) sea level rise by 2100—more melting from Greenland/Antarctica

“Ash Wednesday Storm” Harvey Cedars, March 1962

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

Flood Stage 3 of 7 largest floods since 2004

Warmer ↓ More Evaporation Warmer ↓ More Precipitation

New Brunswick, April 16, 2007 John 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.” days per year over 90ºF days per year over 100ºF Changes in number of days with heat waves from UCS Northeast Climate Impacts Assessment

Future Emissions Scenarios All scenarios show increasing emissions during next several decades Some scenarios show decreased emissions in latter half of 21 st century Even with aggressive reductions in emissions, CO 2 would rise to 2x preindustrial 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 efficiency b) capture and sequester CO 2 from fossil fuel burning c) increase nuclear power generation d) build more wind turbines and solar power systems

Billion of Tons of Carbon Emitted per Year Currently projected path Flat path Historical emissions 1.9  GtC/y 7 GtC/y Seven “wedges” “Wedges” O Source: S. Pacala and R. Socolow, Princeton Univ.

15 Different Technologies Already in the Marketplace 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 22 nd 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 ↓ More Evaporation Warmer ↓ More Precipitation

LikelyMore likely than notLikely Increased incidence of extreme high sea level (excludes tsunamis) LikelyMore likely than not Likely in some regions since 1970 Intense tropical cyclone activity increases LikelyMore likely than not Likely in many regions since 1970s Area affected by droughts increases Very likelyMore likely than notLikely Heavy precipitation events. Frequency (or proportion of total rainfall from heavy falls) increases over most areas Very likelyMore likely than notLikely Warm spells / heat waves. Frequency increases over most land areas Virtually certainLikely (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, /science Dashed lines and gray shading are 2001 TAR projections. Colored lines are observations. While CO 2 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 21 st 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