December 4, 2007
Contact: Tom Steinfeldt, (703) 516-4146
REPORT EXAMINES U.S. REGIONAL IMPACTS OF CLIMATE CHANGE
ADAPTATION SEEN AS A KEY RESPONSE
As the nations of the world gather this week in Bali, Indonesia, to work on a global agreement to reduce greenhouse gas emissions, the Pew Center on Global Climate Change today released a new report examining key impacts of climate change that are likely to affect different areas of the United States. The report, “Regional Impacts of Climate Change: Four Case Studies in the United States,” assesses particular climate vulnerabilities in the Midwest, West, Gulf Coast, and Chesapeake Bay regions.
The report provides useful information about particular impacts in different regions of the United States, as well as a more general perspective on the types of challenges decision-makers will face in developing workable responses to varied climate impacts. Each study also considers non-climatic factors, such as development and management practices that are likely to exacerbate our vulnerability to climate change.
The four studies are:
• The Heat is On: Climate Change and Heatwaves in the Midwest by Kristie L. Ebi of ESS and Gerald A. Meehl of the National Center for Atmospheric Research;
• The Importance of Climate Change for Future Wildfire Scenarios in the Western United States by Dominique Bachelet of Oregon State University and James M. Lenihan and Ronald P. Neilson of the U.S. Forest Service;
• Gulf Coast Wetland Sustainability in a Changing Climate by Robert R. Twilley of Louisiana State University; and
• Ramifications of Climate Change for Chesapeake Bay Hypoxia by Donald F. Boesch, Victoria J. Coles, David G. Kimmel and W. David Miller of the University of Maryland Center for Environmental Science.
The report’s four case studies offer key insights to issues that are likely to affect different regions in the U.S., including:
- Midwestern cities are very likely to experience more frequent, longer, and hotter heatwaves
- Wildfires are likely to increase in the West, continuing a dramatic trend already in progress.
- Gulf Coast wetlands provide critical natural services to humanity, but sustaining these already fragile ecosystems will be increasingly difficult in the face of climate change.
- The Chesapeake Bay may respond to climate change with more frequent and larger low-oxygen “dead zone” events that damage fisheries and diminish tourist appeal.
The authors find that well-considered assumptions about regional climate change should be incorporated into development and management plans based on a range of plausible projections. Studying regions with different vulnerabilities will provide insights and methods for conducting assessments in other regions and sectors.
“The degree to which we can adapt to the consequences of climate change will be determined in large part by the policies and management practices we put in place today,” said Pew Center President Eileen Claussen, “It is clear that we are already seeing changing conditions, and there is a real urgency for strong national and international policy action.” This report offers insights into how we can adapt to a variety of major impacts that we can expect to face now and in decades to come
Historically, risk management strategies have relied on the past as a guide to the future. But with global climate change, the future will no longer resemble the past. The report finds that adaptation measures will have to be a critical component of any long-term U.S. climate strategy. Managing the impacts of climate change requires that we adapt other human activities so that crucial resources, such as Gulf Coast wetlands or public emergency systems, continue to function effectively.
In a white paper released earlier this year, the Pew Center examines specific adaptation measures currently underway at the state level. This paper, “Adaptation Planning – What U.S. States and Localities are Doing,” looks at state and local adaptation efforts and highlights five states with plans already in place and the six additional states considering such measures.
For more information about global climate change and the activities of the Pew Center, visit www.c2es.org.
IPCC AR4 Summary for Policymakers
Released on November 17, 2007, the Summary for Policymakers of the IPCC Fourth Assessment Synthesis Report represents the IPCC’s most comprehensive and definitive statement to date on climate change. The report presents the key findings of the three Working Group reports released earlier this year by the Nobel Peace Prize winning-IPCC.
The following are some of the key highlights addressed in the Synthesis Report:
- There is strong certainty that most of the observed warming of the past half-century is due to human influences, and a clear relationship between the growth in manmade greenhouse gas emissions and the observed impacts of climate change.
- The climate system is more vulnerable to abrupt or irreversible changes than previously thought.
- Avoiding the most serious impacts of climate change -- including irreversible changes – will require significant reductions in greenhouse gas emissions.
- Mitigation efforts must also be combined with adaptation measures to minimize the risks of climate change.
The Synthesis Report is the fourth and final installment of the Fourth Assessment Report. The previous three installments published earlier this year examined the physical science basis for climate change, the impacts of global climate change, and the solutions to global climate change, particularly options for reducing greenhouse gas emissions.
November 19, 2007
The latest IPCC report underscores the need for immediate and sustained action to reduce greenhouse gas emissions, both in the United States and globally. In the United States, many states are demonstrating strong leadership, and I am confident Congress is on the path to enacting a comprehensive mandatory policy in the near future.
Globally, 2008 marks a significant milestone as the Kyoto commitments take effect. But many already have their sights set on a post-Kyoto framework, and steps toward a new international agreement will be the key issue before negotiators next month in Bali.
The ideal outcome from Bali would be a clear mandate to negotiate a comprehensive post-2012 agreement establishing fair, effective, and binding commitments for all major economies. Unfortunately, despite the latest wakeup call from the IPCC, it appears that the United States and some other key governments are not yet prepared to negotiate real commitments. Even if a clear negotiating mandate isn’t possible, it is imperative that any process launched in Bali leave the door open to negotiating commitments. That way, when a new U.S. administration takes office, governments can quickly get down to the business of forging an effective and durable post-2012 framework.
Current Understanding of Antarctic Climate Change
At a time of dramatic warming and rapid sea ice decline in the Arctic, Antarctica has cooled slightly and sea ice has increased around it. Recent scientific progress in understanding how two distinct processes affect Antarctic climate reconciles these seemingly contradictory trends at the Earth’s poles. In a nutshell, the difference arises from (1) a weak response to increasing greenhouse gases and (2) a cooling effect of the stratospheric ozone hole—both unique to the southern hemisphere.
That is not to say that the southern hemisphere is exempt from global warming. As in the north, the southern hemisphere as a whole has warmed over the past half century, but at a slower rate than in the north (Trenberth et al. 2007). The southern hemisphere has much less land surface and more ocean surface than the northern hemisphere; ocean surfaces warm more slowly than land because more energy is required to heat water, and because ocean mixing transports much of the heat downward away from the surface (Parkinson 2004; Levitus et al. 2005). In fact, the signal of human-induced ocean warming has been detected to a depth of at least 700 meters (Barnett et al. 2005). As in the north, southern-hemisphere warming has been greater at mid-latitudes than at the equator, but the high latitudes around Antarctica have cooled over the past four decades (Chapman and Walsh 2007; Parkinson 2006). Because Antarctica occupies only five percent of the surface area of the southern hemisphere, there is no contradiction in this relatively small region cooling as the hemisphere warms overall. Antarctica is among a minority of regions with unique local climate conditions that currently override the global warming trend, although this situation is likely to change in the future if greenhouse gas concentrations continue to rise (Shindell and Schmidt 2004).
In spite of a moderate overall cooling trend, recent Antarctic climate change results from a mix of countervailing signals. A rapid net loss of sea ice occurred during the 1970s, followed by a slow gain. The geographic distribution of sea ice has changed, with the east gaining and the west losing sea ice. The gains and losses are each larger than the overall trend, indicating a high degree of variability and change in the Antarctic sea ice (Parkinson 2006). Scientists were surprised to discover recently that the land-based Antarctic ice sheet, which stores 60 percent of the earth’s fresh water—the equivalent of 70 meters (228 feet) of sea level rise—has been losing slightly more ice each year than it is gaining (Shepherd and Wingham 2007). Most of the ice loss is from the West Antarctic Ice Sheet, the margins of which lie in the ocean (Velicogna and Wahr 2006). Warming of the ocean appears to be eroding this ice sheet at its edges (Shepherd et al. 2004; Rignot and Kanagaratnam 2006). Reaching northward from West Antarctica into the mid-latitudes, the Antarctic Peninsula has experienced the most dramatic warming in the region (Chapman and Walsh 2007; Turner et al. 2005). In a preview of the possible consequences of ice sheet erosion by the warming Southern Ocean, the Larsen B ice shelf, which was attached to the peninsula, disintegrated suddenly in February 2002; as a result, the land-based ice behind the shelf began to flow more quickly into the sea (Scambos et al. 2004). Scientists infer that widespread warming in West Antarctica could lead to many such events in the future, potentially leading to dramatic acceleration of global sea level rise (Alley et al. 2005). Clearly, the Antarctic climate is not changing monotonically in a single direction.
Still, while every other continent on Earth has experienced a clear warming trend over the past five decades (Trenberth et al. 2007), Antarctica—the fifth largest continent—has shown no clear trend
(Chapman and Walsh 2007). There are several key differences between the Arctic and the Antarctic that act in concert to explain the climatic departure between the two regions. Two of the most important factors are the predictably weak warming signal in the Antarctic compared to the Arctic, and the cooling effect of the human-induced stratospheric ozone hole above Antarctica.
As predicted by climate models, the southern hemisphere has warmed less than the northern hemisphere. The warming has occurred predominantly during the winter, and even Antarctica has warmed slightly during the winter, despite its average cooling across all seasons (Chapman and Walsh 2007). Winter is the time of year that climate models show the largest response to increasing greenhouse gas concentrations. So, even though the warming signal is weak, the seasonal pattern is consistent with the human-enhanced greenhouse effect. Since Antarctic winters are much colder than necessary to freeze seawater, a little wintertime warming is insufficient to induce large-scale losses of sea ice without concurrent warming during the summer. In an experiment using a climate model to simulate global sea ice change over a century as a result of increasing atmospheric greenhouse gases, antarctic sea ice decreased by only 10%, while arctic sea ice decreased by 60% (Parkinson 2004). It is not surprising, therefore, that Antarctic sea ice has not mirrored the rapid decline of arctic sea ice.
But Antarctica is cooling and antarctic sea ice is expanding—something more than regionally weak global warming is afoot. That other factor is the ozone hole in the upper atmosphere (stratosphere) above Antarctica. Over the past four decades, the southern Westerlies—a ring of wind that encircles the southern hemisphere between 30° and 60° latitude—have become more intense and have moved closer to the South Pole in an ever-tighter ring around Antarctica. Whenever the Westerlies intensify—regardless of the cause—Antarctica tends to cool because surface air pressure inside the ring decreases (Marshall 2006). This is called adiabatic cooling and is the same reason that the temperature drops as one climbs a mountain. Although scientists are just beginning to study the physical mechanisms by which changes in the stratosphere affect ground-level climate (Baldwin et al. 2007), observations and model results both indicate that the greater amount of stratospheric ozone depletion over the South Pole compared to mid-latitudes has caused the southern Westerlies to shift poleward and intensify (Gillett and Thompson 2003; Shindell and Schmidt 2004). Since ozone depletion is strong over Antarctica but weak over the Arctic (Solomon et al. 2007), this strong cooling effect is unique to Antarctica.
To summarize, surface warming from the greenhouse effect is weaker in the southern hemisphere than in the northern hemisphere, whereas cooling from stratospheric ozone depletion is stronger in the south than in the north. Consequently, the Arctic has warmed dramatically, even as the Antarctic has experienced a small cooling trend. Climate models reproduce this pattern when they are driven by both greenhouse gas increases and stratospheric ozone depletion (Gillett and Thompson 2003; Shindell and Schmidt 2004). Hence, the present cooling of Antarctica is consistent with the rest of the Earth’s surface warming in response to rising greenhouse gas concentrations.
The stratospheric ozone layer filters out harmful ultraviolet radiation from incoming sunlight. To protect public health and natural ecosystems, an international treaty—the Montreal Protocol—is phasing out the release of ozone-depleting chemicals to the atmosphere. According to climate models that correctly simulate the current cooling trend in Antarctica, if greenhouse gases continue to rise as the ozone layer recovers in future decades, the warming effect of greenhouse gases will begin to outweigh the cooling effect of ozone depletion (Shindell and Schmidt 2004). The result would be widespread warming in Antarctica, with attendant declines in sea ice and accelerated loss of land-based ice, with the latter contributing to accelerated sea level rise.
Alley, R.B., P.U. Clark, P. Huybrechts, and I. Joughin. 2005. Ice-sheet and sea-level changes. Science 310:456-460.
Baldwin, Mark P., Martin Dameris, and Theodore G. Shepherd. 2007. How Will the Stratosphere Affect Climate Change? Science 316 (5831):1576-1577.
Barnett, T. P., D. W. Pierce, K. M. AchutaRao, P. J. Gleckler, B. D. Santer, J. M. Gregory, and W. M. Washington. 2005. Penetration of human-induced warming into the world's oceans. Science 309:284-287.
Chapman, W.L., and J.E. Walsh. 2007. A synthesis of Antarctic Temperatures. Journal of Climate 20:4096-4117.
Gillett, N., and D.W.J. Thompson. 2003. Simulation of Recent Southern Hemisphere Climate Change. Science 302:273-275.
Levitus, S., J. Antonov, and T. Boyer. 2005. Warming of the world ocean, 1955-2003. Geophysical Research Letters 32:L02604, doi:10.1029/2004GL021592.
Marshall, G.J. 2006. Half-century seasonal relationships between the Southern Annular Mode and Antarctic temperatures. International Journal of Climatology 27:doi:10.1002/joc.1407.
Parkinson, C.L. 2004. Southern Ocean sea ice and its wider linkages: insights revealed from models and observations. Antarctic Science 16:387-400.———. 2006. Earth's cryosphere: Current state and recent changes. Review of Environment And Resources 31:33-60.
Rignot, E., and P. Kanagaratnam. 2006. Changes in the velocity structure of the Greenland ice sheet. Science 311:986-990.
Scambos, T.A., J.A. Bohlander, C.A. Shuman, and P. Skvarca. 2004. Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophysical Research Letters 31:L18402, doi:10.1029/2004GL020670.
Shepherd, A., and D. Wingham. 2007. Recent sea level contributions of the Antarctic and Greenland ice sheets. Science 315:1529-1532.
Shepherd, A., D. Wingham, and E. Rignot. 2004. Warm ocean is eroding West Antarctic Ice Sheet. Geophysical Research Letters 31:L23402, doi:10.1029/2004GL021106.
Shindell, D.T., and G.A. Schmidt. 2004. Southern Hemisphere climate response to ozone changes and greenhouse gas increases. Geophysical Research Letters 31:L18209, doi:10.1029/2004GL020724.
Solomon, S., R.W. Portmann, and D.W.J. Thompson. 2007. Contrasts between Antarctic and Arctic ozone depletion. Proceedings of the National Academy of Sciences USA 104:445-449.
Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A.K. Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden, and P. Zhai. 2007. Observations: surface and atmospheric climate change. In Climate Change 2007: The Physical Science Basis, edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M.Tignor and H. L. Miller. Cambridge, United Kingdom and New York, N.Y., USA: Cambridge University Press.
Turner, J., S.R. Colwell, G.J. Marshall, T.A. Lachlan-Cope, A.M. Carleton, P.D. Jones, V. Lagun, P.A. Reid, and S. Iagovkina. 2005. Antarctic climate change during the last 50 years. International Journal of Climatology 25:279-294.
Velicogna, I., and J. Wahr. 2006. Measurements of time-variable gravity show mass loss in Antarctica. Science 311:1754-1756.
The Arctic ice cap declined to a record minimum size in summer 2007. Studies indicate this accelerated shrinkage of Arctic sea ice may be in response to a strong warming trend and that the climate reacts more strongly to a given amount of global warming than generally believed.
The Arctic ice cap consists of a continent-sized sheet of sea ice that floats at the surface of the Arctic Ocean. During the dark of winter, the ice cap covers nearly the entire Arctic Ocean, but during the summer constant sunlight melts the edges of the ice cap, causing it to shrink in area. This annual shrinking begins in early spring and progresses into mid-September, when the extent of the ice cap reaches its summertime minimum and begins to grow again as the sun sets for the year and the chill of winter returns. Since 1979, the extent of the Arctic sea ice has been monitored using satellite observations. During this time, the September minimum extent has declined on average as the Arctic has warmed. Since 2000, there has been a series of record-breaking low annual minima, with 2002, 2005, and 2007 each establishing new records. View Graph
On August 17, 2007, the National Sea Ice Data Center (NSIDC) reported: “Arctic sea ice surpassed the previous single-day (absolute minimum) record for the lowest extent ever measured by satellite.” One month later, the NSIDC reported that the ice cap had reached it annual minimum size (Figure 1), which was “4.13 million square kilometers (1.59 million square miles), compared to 5.32 million square kilometers (2.05 million square miles) in 2005.” Compared to the long-term average between 1979 and 2000, The 2007 minimum “was lower by 2.61 million square kilometers (one million square miles), an area approximately equal to the size of Alaska and Texas combined, or the size of ten United Kingdoms.” (NSIDC, 2007b).
The wintertime maximum area of the ice cap occurs in March and has also been shrinking. The annual maximum sea ice extent reached record-breaking lows in three consecutive winters (2004-2006). In March 2007, the maximum extent was the second lowest on record after 2006. Regarding this observation, NSIDC scientist Walt Meier said, “This year's low wintertime extent is another milestone in a strong downward trend. We're still seeing near-record lows and higher-than-normal temperatures. We expect the downward trend to continue in future years” (NSIDC, 2007a).
In recent months, some important peer-reviewed studies have been published on the observed and projected shrinkage of the Arctic ice cap. In April, scientists from NSIDC and the National Center for Atmospheric Research published a study documenting from long-term observations that climate models underestimate the rate of Arctic sea ice loss (Stroeve et al., 2007). Observed loss of sea ice from 1953 to 2006 occurred three times faster than the average rate projected for the same period by 18 of the latest generation of climate models used by the Intergovernmental Panel on Climate Change (IPCC). According to a recent review of the scientific evidence, the observed ice loss “is best viewed as a combination of strong natural variability… and a growing radiative forcing associated with rising concentrations of atmospheric greenhouse gases…” (Serreze et al., 2007).
This summer, the initial rate of Arctic sea ice decline was similar to previous record-breaking years, but in late June and early July there was a dramatic surge in the rate of loss that led to the early arrival of the record-low sea ice extent reached in August (Figure 2). Regarding this surge, the NSIDC said, “…sea ice declined at a pace of up to 210,000 square kilometers (81,081 square miles) per day, or the equivalent of an area the size of Kansas each day. This rate was unprecedented in the satellite record…” (NSIDC, 2007b). View Graph
The cause of this surge is unclear, but is consistent with recent modeling research suggesting that sudden, extreme acceleration of shrinkage may be an inherent response of Arctic sea ice to a strong warming trend (Holland et al., 2006). In this study, about half of the model projections exhibited sudden accelerations in sea ice loss. In the model projections where such events occurred, trends in ice loss were four times faster than in projections without abrupt accelerations. If such accelerations are inherent to the response of sea ice to persistent warming, the Arctic could be ice free during the summer well before the end of this century (Serreze et al., 2007), a condition that has not existed for at least one million years and probably much longer (Overpeck et al., 2005).
The loss of Arctic sea ice is not the only aspect of climate change that has been underestimated by projections. Recent observations indicate that climate models have underestimated ice loss from the Greenland and Antarctic ice sheets (Shepherd & Wingham, 2007), ice loss from mountain glaciers (Meier et al., 2007), the rate of global sea level rise (Rahmstorf et al., 2007), change in global precipitation (Wentz et al., 2007; Zhang et al., 2007), and response of northern forests to warming (Soja et al., 2007). All of these changes were predicted before they were detected, but they are occurring sooner or more rapidly than expected (Engelhaupt, 2007). Although there are probably multiple reasons for underestimating climate change and ecosystem responses to it, inadequately treated positive feedbacks (amplifying factors within the climate system itself) are probably involved (Pittock, 2006).
The unexpectedly rapid change in Arctic sea ice and other climate processes suggests that the climate reacts more strongly to a given amount of global warming than scientists have calculated. As a result, risks from future climate change are likely greater than scientists have generally believed, and existing climate change projections might best be viewed as the minimum changes that humanity should expect.
Engelhaupt, E. 2007. Models underestimate global warming impacts.
Environmental Science & Technology, 41, 4488-4489.
Holland, M. M., Bitz, C. M. & Tremblay, B. 2006. Future abrupt reductions in the summer Arctic sea ice. Geophysical Research Letters, 33, L23503, doi:10.1029/2006GL028024.
Meier, M. F., Dyurgerov, M. B., Rick, U. K., O’Neel, S., Pfeffer, T., Anderson, R. S., Anderson, S. P. & Glazovsky, A. F. 2007. Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century. Science, 317, 1064-1067.
NSIDC. 2007a. Arctic Sea Ice Narrowly Misses Wintertime Record Low. National Sea Ice Data Center. Available online: http://nsidc.org/news/press/ 20070403_winterrecovery.html
NSIDC. 2007b. Arctic Sea Ice News Fall 2007. National Sea Ice Data Center. Available online: http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html.
Overpeck, J. T., Sturm, M., Francis, J. A., Perovich, D. K., Serreze, M. C., Benner, R., Carmack, E. C., III, F. S. C., Gerlach, S. C., Hamilton, L. C., Hinzman, L. D., Holland, M., Huntington, H. P., Key, J. R., Lloyd, A. H., MacDonald, G. M., McFadden, J., Noone, D., Prowse, T. D., Schlosser, P. & Vörösmarty, C. 2005. Arctic System on Trajectory to New, Seasonally Ice-Free State. Eos, 86, 309-316.
Pittock, B. A. 2006. Are Scientists Underestimating Climate Change? Eos: Transactions of the American Geophysical Union, 34, 340-341.
Rahmstorf, S., Cazenave, A., Church, J. A., Hansen, J. E., Keeling, R. F., Parker, D. E. & Somerville, R. C. J. 2007. Recent climate observations compared to projections. Science, 316, 709 (doi:10.1126/science.1136843).
Serreze, M. C., Holland, M. M. & Stroeve, J. 2007. Perspectives on the Arctic’s shrinking sea-ice cover. Science, 315, 1533-1536.
Shepherd, A. & Wingham, D. 2007. Recent sea-level contributions of the Antarctic and Greenland ice sheets. Science, 315, 1529-1532.
Soja, A. J., Tchebakova, N. M., French, N. H. F., Flannigan, M. D., Shugart, H. H., Stocks, B. J., Sukhinin, A. I., Parfenova, E. I., III, F. S. C. & Jr., P. W. S. 2007. Climate-induced boreal forest change: Predictions versus current observations. Global and Planetary Change, 56, 274-296.
Stroeve, J., Holland, M. M., Meier, W., Scambos, T. & Serreze, M. 2007. Arctic sea ice decline: Faster than forecast. Geophysical Research Letters, 34, L09501, doi: 10.1029/2007GL029703.
Wentz, F. J., Ricciardulli, L., Hilburn, K. & Mears, C. 2007. How Much More Rain Will Global Warming Bring? Science, doi:10.1126/science.1140746.
Zhang, X., Zwiers, F. W., Hegerl, G. C., Lambert, F. H., Gillett, N. P., Solomon, S., Stott, P. A. & Nozawa, T. 2007. Detection of human influence on twentieth-century precipitation trends. Nature, 448, 461-465.
IPCC AR4 WGIII: "Mitigation of Climate Change"
The third installment to the IPCC Fourth Assessment Report was released May 4, 2007. The WGIII report analyzes mitigation options for the main economic sectors in the near-term. It also provides information on long-term mitigation strategies, paying special attention to implications of different short-term strategies for achieving long-term goals. This installment also addresses the relationship between mitigation and sustainable development.
The report from Working Group III on mitigation of climate change answers the following questions:
- What have been the greenhouse gas emission trends in the last three decades?
- What can we expect for energy and emission trends in the next thirty years?
- What are the options for GHG mitigation in the short and medium term, across different economic sectors (until 2030) and in the long-term (beyond 2030)?
- How do the time scales of climate system responses relate to the time scales for mitigation and adaptation?
- What are the opportunities for integrating sustainable development and climate change mitigation activities?
Statement by Eileen Claussen, President, Pew Center on Global Climate Change
May 4, 2007
The most recent IPCC working group report provides the latest stark evidence that emissions around the world continue to grow at an alarming rate. We must begin now to put in place the policies and technologies that will provide alternative ways to power our economies and satisfy the world's thirst for energy. We can solve this problem, but only if we start now.
To help more kids better understand global warming, we collaborated with Nickelodeon to research children's and parents' attitudes and behaviors toward the environment.
There's a lot you can learn about global warming. To help, this page provides answers to six key questions about global warming, how it occurs, and how you can help to stop the process. For more tips on actions people can take, visit our What You Can Do page.
You can also explore other kid-oriented sites from the list on this page.
- Do scientists agree about global warming?
- What is causing global warming?
- What is the difference between "global warming" and "climate change?"
- What will happen if global warming continues?
- What is being done about global warming?
- What can I do about global warming?
Do scientists agree about global warming?
Scientists who study the climate are still arguing about how fast the earth is warming and how much it will warm, but they do agree that the earth is warming and that it will keep warming if we don’t do anything about it.
What is causing global warming?
Scientists agree that the burning of fossil fuels like oil and coal cause greenhouse gases to escape into the air and that these gases are causing most of the warming. Another cause is deforestation (cutting down trees). Trees soak up carbon dioxide, one of the greenhouse gases, from the air.
What is the difference between "global warming" and "climate change?"
"Global warming" refers to the increase of the Earth's average surface temperature, due to a build-up of greenhouse gases in the atmosphere. "Climate change" is a broader term that refers to long-term changes in climate, including average temperature and precipitation.
What will happen if global warming continues?
There are already some changes happening because of global warming. Sea level is rising and some animals are already moving to new homes. It’s already too late to stop global warming completely.
If the warming gets worse, as scientists expect, there may be some kinds of plants and animals that become extinct (disappear completely) because they can’t move to new homes. There may be more storms and floods. Sea level may rise so much that people have to move away from the coasts. Some areas may become too dry for farming.
What is being done about global warming?
Global warming is a very difficult problem to fix. People are having a hard time agreeing on what to do about it. For example, everyone agrees that wasting energy is a bad thing to do. But some people think that the federal government should make laws about it, while other people think it should be up to each person or business to decide what to do.
Many states and businesses in the United States are not waiting until the federal government decides what to do. They have already started working on the problem.
What can I do about global warming?
You don’t have to wait until you are grown to do something about global warming. Scientists agree that the burning of fossil fuels is causing global warming. Since these fuels are burned for energy, and everyone uses energy, everyone can help stop global warming just by using less energy.
Think about the things you do each day that use energy. The lights in your house use electricity. The TV and computer use electricity. The washing machine, dishwasher and dryer all use gas or electricity. Every time you ride in your car, it uses gasoline.
There are some simple things that you can do to help stop global warming:
Wait until you have a lot of clothes to wash before using the washing machine. Don’t use the machine for one item just because it’s your favorite shirt.
Turn off the lights when you leave a room. Use fluorescent bulbs in your room.
Turn off your computer or the TV when you’re not using it. Unplug chargers when not in use.
Close the blinds on a hot day if the sun is shining in. Dress lightly instead of turning up the air conditioning. Or use a fan.
Dress warmly inside your house when it’s cold, instead of turning up the heat.
Bike or walk short distances instead of asking for a ride in a car.
Plant a tree.
Take shorter showers. Heating water uses energy.
Learn more about global warming so you can talk to people about it. See: Could it really happen?
For more tips, click here.
The Intergovernmental Panel on Climate Change (IPCC) was established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. The Fourth Assessment report was released in three installments over the course of 2007, with the final synthesis report published in November 2007. Details on the most current release, including a Pew summary and statement, can be found below.
IPCC Summary For Policymakers to the Fourth Assessment Report
To view each working group's report, as well as our statements and related content, click on the working group's title below
- Summary for Policymakers, Release Date: November 17, 2007
- Working Group III - "Mitigation of Climate Change", Release Date: May 4, 2007
- Working Group II - "Impacts, Adaptation & Vulnerability", Release Date: April 6, 2007
- Working Group I - "The Physical Science Basis", Release Date: February 2, 2007
To view published installments in their entirety, visit the IPCC website.
Scientists from all over the world contributed to the findings discussed in the Fourth Assessment Report. For more information on the work of some of these scientists, visit: National Center for Atmospheric Research.
In 1988, recognizing the problem of global warming, two UN agencies, the World Meteorological Organization and the United Nations Environment Programme, established the Intergovernmental Panel on Climate Change (IPCC). The IPCC does not conduct independent research, rather it convenes climate experts from around the world every five to seven years in order to synthesize the latest climate research findings in peer reviewed and published scientific/technical literature. Visit the IPCC website: www.ipcc.ch.
The IPCC issued comprehensive assessments in 1990, 1996, and 2001; its Fourth Assessment Report (AR4) will be released in installments during 2007. The AR4 is the most comprehensive synthesis of climate change science to date. Experts from more than 130 countries are contributing to this assessment, which represents six years of work. More than 450 lead authors have received input from more than 800 contributing authors, and an additional 2,500 experts reviewed the draft documents.
AR4 will comprise three sections, or working groups, that deal with the scientific basis of global warming (Working Group I), its consequences (Working Group II), and options for slowing the trend (Working Group III). The IPCC will release summaries of the three working group documents over the course of 2007, culminating in the publication of the final “synthesis report” at the end of the year.
IPCC AR4 WGII: "Impacts, Adaptation & Vulnerability"
The second installment to the IPCC Fourth Assessment Report was released April 6, 2007. The Working Group II installment to the report addresses "Impacts, Adaptation and Vulnerability". The WGII report provides a detailed analysis of observed changes in natural and human systems and the relationship between those observed changes and climate change, as well as a detailed assessment of projected future vulnerability, impacts, and response measures to adapt to climatic changes for main sectors and regions.
According to the IPCC, the report from Working Group II on the impacts of climate change answers the following questions:
- What is the current state of knowledge on impacts of climate change?
- What is the state of knowledge on impacts under different levels of adaptation?
- What are the impacts under different levels of mitigation?
- What is the state of knowledge concerning observed effects?
IPCC AR4 WGI: "The Physical Science of Climate Change"
The first installment to the IPCC Fourth Assessment Report was released February 2, 2007. According to the IPCC, the Working Group I Report, "The Physical Science Basis", assesses the current state of knowledge about the natural and human drivers of climate change, reflecting the progress of the climate change science in the observation of the atmosphere, the Earth's surface and oceans. It provides a paleoclimatic perspective and evaluates the Earth's surface and oceans. Main topics include changes in atmospheric composition, observation of various climate parameters, coupling between changes in climate and biogeochemistry, evaluation of models and attribution of climate change.
Working Group I Report, "The physical science basis", assesses the current state of knowledge about the natural and human drivers of climate change, reflecting the progress of the climate change science in the observation of the atmosphere, the Earth's surface and oceans. It provides a paleoclimatic perspective and evaluates future projections of climate change. Main topics include changes in atmospheric composition, observation of various climate parameters, coupling between changes in climate and biogeochemistry, evaluation of models and attribution of climate change..
According to the IPCC, the report from Working Group I on the science of climate change answers the following questions:
- What progress has been made in understanding and attributing climate change?
- What do observations of the atmosphere, oceans, sea level, snow and ice tell us?
- How has climate been behaving in the last hundreds of thousands of years?
- Which are the projections of future changes?