* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Climate Change
Climate change in the Arctic wikipedia , lookup
German Climate Action Plan 2050 wikipedia , lookup
Myron Ebell wikipedia , lookup
2009 United Nations Climate Change Conference wikipedia , lookup
Climate resilience wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Climatic Research Unit email controversy wikipedia , lookup
ExxonMobil climate change controversy wikipedia , lookup
Soon and Baliunas controversy wikipedia , lookup
Heaven and Earth (book) wikipedia , lookup
Michael E. Mann wikipedia , lookup
Effects of global warming on human health wikipedia , lookup
Climate change adaptation wikipedia , lookup
Climate engineering wikipedia , lookup
Citizens' Climate Lobby wikipedia , lookup
Climate change denial wikipedia , lookup
Economics of global warming wikipedia , lookup
Climate governance wikipedia , lookup
Global warming controversy wikipedia , lookup
Future sea level wikipedia , lookup
Fred Singer wikipedia , lookup
United Nations Framework Convention on Climate Change wikipedia , lookup
Climatic Research Unit documents wikipedia , lookup
Climate sensitivity wikipedia , lookup
Carbon Pollution Reduction Scheme wikipedia , lookup
Climate change and agriculture wikipedia , lookup
Climate change in Tuvalu wikipedia , lookup
Global warming hiatus wikipedia , lookup
Politics of global warming wikipedia , lookup
Global Energy and Water Cycle Experiment wikipedia , lookup
Physical impacts of climate change wikipedia , lookup
Global warming wikipedia , lookup
Effects of global warming wikipedia , lookup
Solar radiation management wikipedia , lookup
Effects of global warming on humans wikipedia , lookup
Media coverage of global warming wikipedia , lookup
General circulation model wikipedia , lookup
Climate change in the United States wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Climate change and poverty wikipedia , lookup
Climate change feedback wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Public opinion on global warming wikipedia , lookup
Climate change, industry and society wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
Computer Modeling of the Global Climate & its Role in the Assessment of Climate Change Keith W. Dixon research meteorologist NOAA / Geophysical Fluid Dynamics Laboratory Princeton, NJ NROW IX Albany, New York 7 Nov 2007 My Background • Undergrad & Grad work @ Rutgers Univ. Met. Dept. • Radio Wx with Norm MacDonald in early 80’s – 13 stations in NE US (anyone here remember him?). • Meteorological consulting work in early 80’s. • Research meteorologist at NOAA Geophysical Fluid Dynamics Lab (GFDL) for 20+ years. • Taught undergrad course at Rutgers in late 80’s and early 90s. • Favorite Wx Event: The Megalopolitan Snowstorm of Feb 1983… thunder snow & getting to close Rutgers! My Background • Undergrad & Grad work @ Rutgers Univ. Met. Dept. • Radio Wx with Norm MacDonald in early 80’s – 13 stations in NE US (anyone here remember him?). • Meteorological consulting work in early 80’s. • Research meteorologist at NOAA Geophysical Fluid Dynamics Lab (GFDL) for 20+ years. • Taught undergrad course at Rutgers in late 80’s and early 90s. • Favorite Wx Event: The Megalopolitan Snowstorm of Feb 1983… thunder snow & getting to close Rutgers! My Background • Undergrad & Grad work @ Rutgers Univ. Met. Dept. • Radio Wx with Norm MacDonald in early 80’s – 13 stations in NE US (anyone here remember him?). • Meteorological consulting work in early 80’s. • Research meteorologist at NOAA Geophysical Fluid Dynamics Lab (GFDL) for 20+ years. • Taught undergrad course at Rutgers in late 80’s and early 90s. • Favorite Wx Event: The Megalopolitan Snowstorm of Feb 1983… thunder snow & getting to close Rutgers! Outline: • Part 1) Public Talk – early 2007 vintage A “Science Briefing” on Physical Climate Science… decadal to centennial time scale climate variability and change & the role of climate modeling. • Part 2) Update: Some FAQs, including how physical climate science fits into the expanding scope of “the climate change challenge”. Building upon previous Q&A. Communications challenges. Outline: common thread = separating “signal” from “noise” • The distinction between Climate Change Science & Climate Change Policy (science that is “policy relevant” not “policy prescriptive”) • Looking Back (1860-present): past climate variability & change – an issue of Detection & Attribution (a synthesis of observations, theory & models) • Looking Ahead: Future scenarios and model projections for the 21st century and beyond (climate change commitment… factors in the equation … a matter of scale) • Summary and Q&A • For related info go to: http://www.gfdl.noaa.gov/research/climate/highlights http://www.ipcc.ch (Working Group 1 = WG1) http://www.ametsoc.org/policy/2007climatechange.html http://www.climatescience.gov (US Climate Change Science Program) Outline: common thread = separating “signal” from “noise” • The distinction between Climate Change Science & Climate Change Policy (science that is “policy relevant” not “policy prescriptive”) • Looking Back (1860-present): past climate variability & change – an issue of Detection & Attribution (a synthesis of observations, theory & models) • Looking Ahead: Future scenarios and model projections for the 21st century and beyond (climate change commitment… factors in the equation … a matter of scale) • Summary and Q&A • For related info go to: http://www.gfdl.noaa.gov/research/climate/highlights http://www.ipcc.ch (Working Group 1 = WG1) http://www.ametsoc.org/policy/2007climatechange.html http://www.climatescience.gov (US Climate Change Science Program) Outline: common thread = separating “signal” from “noise” • The distinction between Climate Change Science & Climate Change Policy (science that is “policy relevant” not “policy prescriptive”) • Looking Back (1860-present): past climate variability & change – an issue of Detection & Attribution (a synthesis of observations, theory & models) • Looking Ahead: Future scenarios and model projections for the 21st century and beyond (climate change commitment… factors in the equation … a matter of scale) • Summary and Q&A • For related info go to: http://www.gfdl.noaa.gov/research/climate/highlights http://www.ipcc.ch (Working Group 1 = WG1) http://www.ametsoc.org/policy/2007climatechange.html http://www.climatescience.gov (US Climate Change Science Program) Media Coverage of Climate Change Issue Climate change is a big and complex scientific and political/social issue. The media reports on both aspects – often blending the two. Though a political consensus may not exist in the US, the strong scientific consensus is that we are seeing more signs that human induced climate change is real and that change will become more rapid. Time Magazine April 9, 2001 “Climbing temperatures. Melting glaciers. Rising seas. All over the earth we’re feeling the heat. Why isn’t Washington?” Media Coverage of Climate Change Issue Climate change is a big and complex scientific and political/social issue. The media reports on both aspects – often blending the two. Though a political consensus may not exist in the US, the strong scientific consensus is that we are seeing more signs that human-caused climate change is real and that change will become more rapid. Time Magazine April 9, 2001 “Climbing temperatures. Melting glaciers. Rising seas. All over the earth we’re feeling the heat. Why isn’t Washington?” Not a SCIENTIFIC QUESTION, so I’m not going there in this talk! Media Coverage of Climate Change Issue Climate change is a big and complex scientific and political/social issue. The media reports on both aspects – often blending the two. Though a political consensus may not exist in the US, the strong scientific consensus is that we are seeing more signs that human-caused climate change is real and that change will become more rapid. Time Magazine April 9, 2001 “Climbing temperatures. Melting glaciers. Rising seas. All over the earth we’re feeling the heat. Why isn’t Washington?” Fermenting Froth vs. Scientific Consensus Sources of Scientific Info: Individual peer-reviewed scientific papers… (typically journal articles are officially reviewed by 2 or 3 people, as opposed to dozens or hundreds who are involved in the preparation of large “assessment” reports like IPCC, CCSP, etc.) The ideas contained in the individual papers are bits of the “fabulous fermenting froth*” of scientific investigation. The assessment reports serve to distill the information and communicate the policy relevant bits that stand up. (*paraphrase of Richard Alley during Congressional Hearing of 8 Feb 2007) Climate Change: A Matter of Contending Perspectives (after Mike MacCracken) Different cost/benefit analyses are done by those with these different perspectives, but all are linked to the underlying climate science. The National Media Economics Security Ethics Politics CLIMATE SCIENCE Fossil Fuel Industry Energy Technology Environmental Conservation Local Global Where I kind of fit in… National Security The Media Economics Ethics CLIMATE SCIENCE Politics Energy Technology Environmental Conservation My expertise is in the science of climate change. Fossilphysical Fuel Local Industry (oceans, atmosphere, sea ice, land hydrology… Global not economics, ecosystems, inter-generational ethics or politics) But I can comment on some experiences concerning communicating science info to people in other fields. Some of what is beyond the scope of my expertise… National Security The Media Economics Ethics The science I speak of does not include… Politics CLIMATE SCIENCE Energy Technology Environmental Conservation determiningFossil what is an “unacceptable” or Fuel Local Industry “dangerous” amount of climate change. Global prescribing when & which human responses should be taken. People get their climate science info via the media, who in turn get their info from various sources The The volume of climate change info being reported Media National has increased in recent months, Economicsbut has the Security “signal to noise ratio” of the science content improved? Ethics CLIMATE SCIENCE Politics Energy Technology Environmental Conservation vs. The Scientist as an “Advocate” (of policy, etc.) Goal: using science to promote a particular downstream effect. Fossil Fuel Industry Local vs. The Non-scientistGlobal presenting scientific info vs. The Misinformer with or without scientific credentials Goal: misrepresenting science to promote a particular downstream effect. International Scientific Consensus… Intergovernmental Panel on Climate Change (IPCC) WG1 Summary for Policymakers released 2 Feb 2007 600 authors from 40 countries. Over 620 expert reviewers and a large number of government reviewers (~133 nations). 4th: 2007 3rd: 2001 2nd: 1995 1st: 1990 IPCC WG2 = Impacts; IPCC WG3 = Mitigation http://www.ipcc.ch/SPM2feb07.pdf http://ipcc-wg1.ucar.edu/wg1/wg1-report.html Most climate change discussions focus on changes in surface climate… commonly, global surface air temperature Most climate change discussions focus on changes in surface climate… commonly, global surface air temperature Most climate change discussions focus on changes in surface climate… commonly, global surface air temperature “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 AR4 WG1 SPM, Feb 07 Most climate change discussions focus on changes in surface climate… commonly, global surface air temperature “Warming theobserved climate increase system is in unequivocal, “Most ofofthe globally as is nowtemperatures evident from since observations of increases th century averaged the mid-20 in average ocean temperatures, is global very likely* dueair to and the observed increase in widespread greenhouse melting of snow and ice, and anthropogenic gas concentrations.” rising level.” (*veryglobal likely =average 90-95% sea certainty) IPCC AR4 AR4 WG1 WG1 SPM, Feb 07 -- IPCC Most climate change discussions focus on changes in surface climate… commonly, global surface air temperature “Continued emissions at or above “Most of greenhouse the observedgas increase in globally th century current temperatures rates would cause warming and averaged sincefurther the mid-20 induce changes global climate is verymany likely* due to in thethe observed increasesystem in during the 21stgreenhouse century thatgas would very likely be anthropogenic concentrations.” = 90-95% certainty) larger than (*very those likely observed during the 20th century.” (*very likely = 90-95% certainty)- -IPCC IPCCAR4 AR4WG1 WG1SPM, SPM,Feb Feb0707 The International IPCC & US CCSP (http://www.ipcc.ch) The IPCC is the biggest, but not the only science-based climate assessment game in town… The US CCSP is a presidential initiative that seeks to integrate federal research on climate change. More than 20 synthesis & assessment reports on key topics relevant to decision makers are planned. Joint Statement on Climate Change Eleven National Science Academies - 2005 (including all members of the Group of Eight industrial powers) Their role is to inform & advise. "Climate change is real. There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. … It is likely that most of the warming in recent decades can be attributed to human activities. ... The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. It is vital that all nations identify cost-effective steps that they can take now, to contribute to substantial and long-term reduction in net global greenhouse gas emissions.” http://nationalacademies.org/onpi/06072005.pdf Joint Statement on Climate Change Eleven National Science Academies - 2005 (including all members of the Group of Eight industrial powers) Their role is to inform & advise. "Climate change is real. There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. … It is likely that most of the warming in recent decades can be attributed to human activities. ... The scientific understanding of climate change is now clear to justify nations taking prompt action. It is vital Theirsufficiently physical science statements are consistent with what I present here. that all nations identify cost-effective steps that they can take now, I don’t comment on the policy bits they cover... It’s beyond expertise to contribute to substantial and long-term reduction in netmy global and not my role. greenhouse gas emissions.” http://nationalacademies.org/onpi/06072005.pdf ← If you’re in the DC area, check out this museum. (http://www.koshland-science-museum.org/exhibitgcc ) http://www.ametsoc.org/policy/2007climatechange.html Important Climate Science Questions 1. Is Earth’s climate changing? 2. If so, what is causing the changes? 3. Will the climate change during the 21st century (and beyond)? A Synthesis of Observations, Theory and Numerical Modeling The Climate Model Knowledge Cycle THEORY Knowledge & Understanding Model Development OBSERVATIONS Analysis of Model Results Well Designed Model Experiments Current model resolution 1980s Atmosphere 2 deg. 1990s 2000s OCEAN MODEL RESOLUTION: 1 deg. What is a State-of-the-Art Global Climate Model? The four physical climate components The Next Generation: Earth System Model Atmospheric GCM Sea ice model Ocean GCM Land physics and hydrology Atmospheric GCM Tracer transport and chemistry Ocean ecology and biogeochemistry Sea ice model Ocean GCM Land ecology and biogeochemistry Land physics and hydrology Adding interactive Carbon and Nitrogen Cycling, etc. 1. Is Earth’s climate changing? 2. What is causing the changes? Questions of Detection and Attribution: Detection: establishing that an observed change is significantly different than can be explained by internal variability (separating signal from the noise). Attribution: establishing cause and effect, and assessing alternative hypotheses. 1. Is Earth’s climate changing? Looking Back: Past climate variability & change – an issue of Detection From the 2007 Intergovernmental Panel on Climate Change Report (WG1): “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.” 2. What is causing the changes? A question of Attribution: From the 2007 Intergovernmental Panel on Climate Change Report (WG1): “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.” *very likely = 90-95% certainty 2. What is causing the changes? Carbon Dioxide Observational Evidence for Greenhouse Gas Increases: Methane Nitrous Oxide Variations of the Earth’s Surface Temperature Global surface temperatures over the past 140 years Plateau Late century warming Early century warming (Graph shows temperature changes relative to the 1961-1990 average in oC. Multiply by 1.8 to convert to oF.) 2. What is causing the changes? Variations of the Earth’s Surface Temperature Observed Global Surface Temperatures * Well-mixed greenhouse gases (CO2, CH4, N2O, CFCs { F11, F12, F113, F22}) * Stratospheric O3, * Tropospheric O3 * Tropospheric Aerosols: [Sulfate, Black and Organic Carbon], [Dust and Sea-salt]; * Land-use change (Hurtt et al.) * Solar irradiance variations (Lean et al.) * Volcanic aerosols (Ramachandran et al., Sato et al.) 2. What is causing the changes? Variations of the Earth’s Surface Temperature Observed Global Surface Temperatures Model with D Greenhouse Gases Only (n=3) Model forced only by smoothly varying GHGs yields temperature response that’s smoother than the observed. (this was characteristic of models of the ’80s and early ’90s) * Well-mixed greenhouse gases (CO2, CH4, N2O, CFCs { F11, F12, F113, F22}) * Stratospheric O3, * Tropospheric O3 * Tropospheric Aerosols: [Sulfate, Black and Organic Carbon], [Dust and Sea-salt]; * Land-use change (Hurtt et al.) * Solar irradiance variations (Lean et al.) * Volcanic aerosols (Ramachandran et al., Sato et al.) 2. What is causing the changes? Variations of the Earth’s Surface Temperature Observed Global Surface Temperatures Model with Natural Forcings Only (solar + volcanic, n=3) Model with Natural Forcings is consistent with obs until ~1960… …but can not explain late-century warming 2. What is causing the changes? Variations of the Earth’s Surface Temperature Observed Observed Global Global Surface Surface Temperatures Temperatures “All-Forcings” Model Results (n=5): (7 GHGs, solar, volcanic, multiple aerosols, land use changes) Considering all of these different “forcings”(Natural & Anthropogenic) the model gets both the magnitude of the warming & the decade variations “about right” Global Surface Air Temperatures Goldilocks’ & The 3 Bears Attribution Conclusions: • If we consider only the natural forcings (solar and volcanic), the climate simulation is too cold (don’t have the late 20th century warming signal). •If we consider only the GHGs, the climate simulation gets too hot too fast. •Considering together various types of forcing changes (natural & humaninduced) the model’s 20th century global average temperature simulations are just about right. (1) GHGs (warming) (2) Solar(+/-) (3) Volcanic (cooling) (4) Tropospheric Aerosols (pollutants) (+&-, net -, short lived) Global Surface Air Temperatures Goldilocks’ & The 3 Bears Attribution Conclusions: • The simplified explanation presented here is meant to illustrate the Detection/Attribution process. In reality, much more detailed analysis (with some sophisticated statistical methodologies) have been performed using… • Results from several modeling research centers • Looking at 4-D atmospheric temperatures (regional, vertical) • Similar studies have also looked multiple climate variables, including ocean heat content (80-90% of the heat gained in the past century resides in the ocean) Global Surface Air Temperatures Goldilocks’ & The 3 Bears Attribution Conclusions: • The simplified explanation presented here is meant to illustrate the Detection/Attribution process. In reality, much more detailed analysis (with some sophisticated statistical methodologies) have been performed using… • Results from several modeling research centers • Looking at 4-D atmospheric temperatures (regional, vertical) • Similar studies have also looked multiple climate variables, including ocean heat content (80-90% of the heat gained in the past century resides in the ocean) Global Surface Air Temperatures Goldilocks’ & The 3 Bears Attribution Conclusions: • The simplified explanation presented here is meant to illustrate the Detection/Attribution process. In reality, much more detailed analysis (with some sophisticated statistical methodologies) have been performed using… • Results from several modeling research centers • Looking at 4-D atmospheric temperatures (regional, vertical) • Similar studies have also looked multiple climate variables, including ocean heat content (80-90% of the heat gained in the past century resides in the ocean) Global Surface Air Temperatures Goldilocks’ & The 3 Bears Attribution Conclusions: • The simplified explanation presented here is meant to illustrate the Detection/Attribution process. In reality, much more detailed analysis (with some sophisticated statistical methodologies) have been performed using… • Results from several modeling research centers • Looking at 4-D atmospheric temperatures (regional, vertical) • Similar studies have also looked multiple climate variables, including ocean heat content (80-90% of the heat gained in the past century resides in the ocean) Ocean Heat Content (ANTHRO includes WMGGO3 & AEROSOL) References: • Delworth, T. L., V. Ramaswamy, and G. L. Stenchikov, 2005: The impact of aerosols on simulated ocean temperature and heat content in the 20th century. Geophysical Research Letters, vol 32. • Levitus, S., J. I. Antonov, J. Wang, T. L. Delworth, K. W. Dixon, and A. J. Broccoli, 2001. Anthropogenic warming of Earth's climate system. Science, 292(5515), 267-270. [ONE PAGE SUMMARY] GFDL Model results 2 meters The upper 2 meters of the ocean contains as much heat energy as does the entire column of air above. Schematic of 3-D Ocean Circulation After Gnanadesikan & Hallberg, 2002 Drake Passage S N Simulated Ocean Heat Content Changes Simulated Surface Air Temperature Response vs. Simulated Ocean Heat Uptake Response Simulated Global Avg. Surface Air Temperature Response The “full” model (one with a dynamical ocean model component and realistic bathymetry) Simulated Global Avg. Surface Air Temperature Response Time Lag Warming Commitment The “full” model (one with a dynamical ocean model component and realistic bathymetry) The mixed-layer ocean model (the ocean is only 50m deep ) • ‘Global Warming’ is not globally uniform. • The 3-D ocean plays an important role in influencing both the rate of global surface air temperature warming –and- the geographic patterns of surface warming. • The ocean’s “thermal inertia” is largely due to its high heat capacity and its deep vertical mixing… the ocean sequesters “greenhouse heat” (~80+%). • Model simulations suggest that a significant fraction of the ocean heat content increase is occurring in regions and depths that have not been well-observed in the past. 3. Will the climate change in the 21st Century and beyond? From the 2007 Intergovernmental Panel on Climate Change (IPCC) Report: “Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.” *very likely = 90-95% certainty … But what about the uncertainties? Prediction vs. Projection http://sciencepolicy.colorado.edu/zine/archives/1-29/26/guest.html Prediction versus Projection – Forecast versus Possibility Mike MacCracken U.S. Global Change Research Program A prediction is a probabilistic statement that something will happen in the future based on what is known today. A prediction generally assumes that future changes in related conditions will not have a significant influence. In this sense, a prediction is most influenced by the “initial conditions”. In contrast to a prediction, a projection specifically allows for significant changes in the set of "boundary conditions" that might influence the prediction, creating "if this, then that" types of statements. Thus, a projection is a probabilistic statement that it is possible that something will happen in the future if certain conditions develop. The set of time-varying “boundary conditions” that is used in conjunction with making a projection is often called a scenario, and each scenario is based on assumptions about how the future will develop. Prediction vs. Projection http://sciencepolicy.colorado.edu/zine/archives/1-29/26/guest.html Prediction versus Projection – Forecast versus Possibility Mike MacCracken U.S. Global Change Research Program A prediction is a probabilistic statement that something will happen in the future based on what is known today. A prediction generally assumes that future changes in related conditions will not have a significant influence. In this sense, a prediction is most influenced by the "initial conditions“. In contrast to a prediction, a projection specifically allows for significant changes in the set of "boundary conditions" that might influence the prediction, creating "if this, then that" types of statements. Thus, a projection is a probabilistic statement that it is possible that something will happen in the future if certain conditions develop. The set of boundary conditions that is used in conjunction with making a projection is often called a scenario, and each scenario is based on assumptions about how the future will develop. 3. Will the climate change in the 21st Century and beyond? From the 2007 Intergovernmental Panel on Climate Change (IPCC) Report: “Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.” *very likely = 90-95% certainty … But what about the uncertainties? Uncertainties In Climate Change Projections Two broad types of uncertainties: 1) What will be the future concentrations of greenhouse gases in the atmosphere? (depends on population size, economic growth, energy use efficiency and development of alternative energy sources) 2) How will the climate system respond to the changes in greenhouse gases? (the computer models are incomplete & are not perfect) Model projections following 3 different “If…Then” 21st cent. 9F emissions scenarios and the “Committed Climate Change” scenario. --- 4.5F Shaded areas show +/- 1 std. dev. of model runs. 0F T=PxGxExC+d T: Total annual greenhouse gas emission rate P: Population size G: per capita Gross Domestic Product $ E: Energy use per $ of GDP C: GHG emissions per unit energy use d: Deforestation effects * And since most of the major anthropogenic greenhouse gases stay in the atmosphere for several years to more than a century, where they enter the atmosphere doesn’t matter to the climate system. Uncertainties In Climate Change Projections The smaller the spatial scale, the greater the uncertainty. In other words, we have more confidence in projections about how the climate may change over large areas (for example, the Arctic vs. the tropics… temperatures over mid-latitude oceans vs. mid-latitude land) than we do for individual states or congressional districts. Uncertainties In Climate Change Projections The smaller the spatial scale, the greater the uncertainty. Implications: People (scientists, policymakers, the general public) tend to place global warming on their “radar screens” on the basis of convincing physical science evidence on the global and very large scale – the scales that we have the most confidence in. However, once climate change is a matter they give attention to, most people then ask about smaller scale impacts (and not just the physical climate). • GFDL CM2.1 model-simulated change in seasonal mean surface air temperature from the late 20th century (1971-2000 average) to the middle 21st century (2051-2060). The left panel shows changes for June July August (JJA) seasonal averages, and the right panel shows changes for December January February (DJF). The simulated surface air temperature changes are in response to increasing greenhouse gases and aerosols based on a "middle of the road" estimate of future emissions known as IPCC SRES A1B. Warming is projected to be larger over continents than oceans, and is largest at high latitudes of the Northern Hemisphere during Northern Hemisphere winter. Will the Wet Get Wetter & The Dry Drier? Will the Wet Get Wetter & The Dry Drier? Communication Challenges? Sea Level Rise In a Warming World One can read about the implications of sea level rise on US infrastructure in the popular press… Some of which may not sufficiently distinguish between persistent innundation due to longterm sea level rise vs. flooding during storm surges and high tides on top of sea level rise. A once in 100 year flooding event may become a once in 50 yr or 20 yr or 5 yr event… Paraphrasing the IPCC AR4 Working Group 1 Summary For Policymakers (Feb. 2007) • Ocean warming and sea level rise will continue for centuries. Long time scales … like turning around a supertanker • Ice flow dynamics could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. However, understanding of these ice sheet processes is limited. The 2 Major Reasons for Global Sea Level Change 1) Because ocean water expands when it warms. Our climate models directly simulate the thermal expansion effect. 2) Because land ice is adding water to the ocean. Our climate models only estimate the land ice effect. Reducing sea level projection uncertainties requires improvements in scientific understanding & a commitment of computer modeling resources. In other words, A Synthesis of Observations, Theory & Modeling. NASA graphic 24” 12” 0” COMMITTED CHANGE A Single GFDL CM2.1 Coupled Climate Model Projection SRES A1B CHANGE The Science of Sea Level Rise In a Warming World Attribution across the scales of climate Q: What does the above statement that appeared in the Boston Globe’s opinion section have in common with… Attribution across the scales of climate Research [...] currently in press with the Journal of Climate, describes the tropical multi-decadal signal and shows that it accounts for the entire inter-related set of conditions that controls hurricane activity for decades at a time." Attribution across the scales of climate A: They both assert with 100% certainty that hurricane events in the Atlantic are either entirely due to anthropogenic climate change or have absolutely nothing to do with humaninduced climate change. The level of uncertainty for this topic is such that a forecast of either 0% or 100% probability is irresponsible. Forest fires occur due to natural causes (e.g., lightning), otherwise there would be no forest fires in uninhabited areas, past or present. • So does the fact that forest fires occur naturally mean that Smokey is a liar, and that people can not cause forest fires? • Or conversely, if Smokey’s right, then are all forest fires a result of humans? Is the problem that statement like this… • no one specific weather event, such as [this recent spell of warm weather in the East], can be uniquely attributed directly to global warming. …is misinterpreted as being equivalent to… • no one specific weather event, such as [this recent spell of warm weather in the East], can be uniquely attributed directly to global warming, and therefore we can say it is entirely unrelated to global warming. If that is the case, then there are analogies that might help reinforce the distinction. ”It's very dangerous to blame climate for weather," says Richard Alley, a professor of geosciences at Penn State University. But he doesn't let climate change off the hook when discussing our warm winter. "No, we didn't cause it, but we made it more likely," he concludes. It's like rolling loaded dice in a craps game. Natural modulation of ENSO in a 2000yr coupled GCM run Annual Cycle } ENSO (somewhat irregular period) Courtesy Andrew Wittenberg, NOAA/GFDL Natural modulation of ENSO in a 2000yr coupled GCM run 2000 yr & 400 yr means 100 yr means 25 yr means } Courtesy Andrew Wittenberg, NOAA/GFDL Natural modulation of ENSO in a 2000yr coupled GCM run 2000 yr & 400 yr means 100 yr means 25 yr means ~ length of satellite record Courtesy Andrew Wittenberg, NOAA/GFDL Decadal Atlantic MOC Predictability Building some small ensembles by tweaking initial conditions: The CM2.1 model produces a separate restart file for each of its 4 main subcomponents. In our first line of inquiry, we generated ensembles of 20 year long runs by mixing atmospheric restarts drawn from days >5 days and < 1 month from the 1 Jan initialization used for the ocean, land & sea ice restarts. For example… ocean land sea ice 1 Jan 1001 generating a ten member ensemble atmos 07 Dec 1000 12 Dec 1000 17 Dec 1000 22 Dec 1000 27 Dec 1000 06 Jan 1001 11 Jan 1001 16 Jan 1001 21 Jan 1001 26 Jan 1001 ?? Will the ensemble members suggest Atl. MOC predictability exists over periods of a decade or longer… …or not? And why? Regarding communication of climate change projections… In addition to longer term trend estimates with ranges And statements such For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected… (IPCC AR4 SPM) Might it be valuable to convey information about the possibility of short term (~5-10 yr) cooling or greater short term warming rates that would not be inconsistent with these results? (more so at smaller spatial scales). [analogous to 30%POP forecast?] SUMMARY The strong scientific consensus is that we are seeing more signs that human caused climate change is real and that change will become more rapid in the coming century. However… • Need to think in terms of projection possibilities, not detailed, localized certainties. • We still have a lot to learn about how the climate system works. • As models become more sophisticated, they will include more climate system feedbacks (+ & -). • More work will be required to narrow the range of uncertainties about the future spatial and temporal evolution of climate. • In addition to more knowledge of the climate system, developing more skill at smaller spatial scales will require more computer power. On the science side, the continued synthesis of observations, theory and modeling will help separate the signal from the noise. Computer Modeling of the Global Climate & its Role in the Assessment of Climate Change Keith W. Dixon research meteorologist NOAA / Geophysical Fluid Dynamics Laboratory Princeton, NJ NROW IX Albany, New York 7 Nov 2007 Projections of Future Changes in Climate • For the next two decades a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. • Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected. • Earlier IPCC projections of 0.15 to 0.3 oC per decade can now be compared with observed values of 0.2 oC Projections of Future Changes in Climate There is now higher confidence in projected patterns of warming and other regional-scale features, including changes in wind patterns, precipitation, and some aspects of extremes and of ice. PROJECTIONS OF FUTURE CHANGES IN CLIMATE • Snow cover is projected to contract • Widespread increases in thaw depth most permafrost regions • Sea ice is projected to shrink in both the Arctic and Antarctic • In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century PROJECTIONS OF FUTURE CHANGES IN CLIMATE • Very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent • Likely that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation less confidence in decrease of total number • Extra-tropical storm tracks projected to move poleward with consequent changes in wind, precipitation, and temperature patterns PROJECTIONS OF FUTURE CHANGES IN CLIMATE • Based on current model simulations, it is very likely that the meridional overturning circulation (MOC) of the Atlantic Ocean will slow down during the 21st century. longer term changes not assessed with confidence • Temperatures in the Atlantic region are projected to increase despite such changes due to the much larger warming associated with projected increases of greenhouse gases. PROJECTIONS OF FUTURE CHANGES IN CLIMATE • Anthropogenic warming and sea level rise would continue for centuries due to the timescales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized. • Temperatures in excess of 1.9 to 4.6°C warmer than preindustrial sustained for millennia…eventual melt of the Greenland ice sheet. Would raise sea level by 7 m. Comparable to 125,000 years ago.