Climate Science Primer

Climate Change Primer Tabs

Current Climate Change

Global Warming and Rising CO2

Global average surface temperatures have increased markedly over the last century (Figure 1). Humans have been measuring temperature directly since the mid- 1800’s; these measurements show that temperature increased by 1.53°F (0.85°C ) between 1880 and 2012, and that the rate of warming is increasing (IPCC 2013 Ch. 2). With the exception of 1998, the 10 warmest years in the 134-year record all have occurred since 2000, with 2010 and 2005 ranking as the warmest years on record (NASA GIS 2014).  Although 1.53°F may not seem like a large temperature change, on a global scale this has huge implications for many of the earth’s processes that affect ecosystems and humans. To put the number in perspective, many scientists think that temperature increases in excess of 3.6°F (2.0°C) relative to 1980-1999 will create outcomes dangerous to human civilization; others say that even lesser increases would be enough to do this (Anderson & Bows 2011).

Figure 1 - Global temperature trend from 1880 to present, compared to a base period of 1951-1980. Global temperatures continue to rise, with the decade from 2000 to 2009 as the warmest on record Data from NASA's Goddard Institute for Space Studies (GISS).

Excess greenhouse gases in the atmosphere are a measureable and significant contributor to global warming, and their concentrations have steadily increased over the past century (IPCC 2013 Ch. 2). Carbon dioxide (CO2), the most important greenhouse gas in terms of climate change, has been measured directly since 1958. Additionally, atmospheric levels of CO2 can be reconstructed for hundreds of thousands of years into the past using methods such as analyzing air bubbles trapped in ice. CO2 concentration in late 2013 was at 395 parts per million, a level that is higher than at any point during the past 800,000 years (Global Carbon Budget 2014; Figure 2). Growth rates of atmospheric CO2 are still high; CO2 emissions from fossil fuel burning and cement production  in 2013 were the highest in any other year of human history, 61% higher than CO2 emissions in 1990 (Global Carbon Budget 2014).

 

Figure 2 - Human society is entering uncharted territory as atmospheric levels of greenhouse gases continue to rise. Today’s carbon dioxide levels are substantially higher than anything that has occurred for more than 800,000 years (last 400,000 years pictured here). Data from NOAA National Climatic Data Center and the Mauna Loa observatory.

Climate Change

For an animated look at how CO2 concentrations have changed over the last 800,000 years, see this video created by the NOAA Earth System Research Laboratory

Rising global temperatures are causing the Earth’s climate patterns to change. Climate can be defined as the "average weather," or the average long-term (multi-decadal) meteorological conditions and patterns for a given area. Changes in climate that are occurring as the planet warms include seasonal and regional changes in temperature and precipitation, (USGCRP 2014 Ch. 2, IPCC 2013 Ch.2), and increasing extreme weather events (IPCC 2011). As an example, precipitation from 1991 to 2012 increased significantly in some parts of the United States including the Great Plains, Northeast, and Midwest, , and declined in other regions during the same time period, particularly parts of the Southwest and Southeast (USGCRP 2014 Ch. 2).

IIn conjunction with temperature and precipitation changes, during the 20th and early 21st centuries there has been a nearly worldwide reduction in glacial mass and extent, a decrease in snow cover in many Northern Hemisphere regions, a decrease in Arctic sea ice thickness and extent, a decrease in the length of river and lake ice seasons, permafrost warming, warmer ocean temperatures, and rising sea levels (IPCC 2013 Summary for policymakers), among other observed changes (Figure 3).


Figure 3 - Multiple observedindicators of a changing climate: a. Observed sea level changes, derived from coastal tide gauge data, and b. Satellite data showing loss of ice sheet mass in Antarctica. The continent of Antarctica has been losing about 147 billion tons of ice per year since 2003. Source: NASA Global Climate Change – Vital Signs of the Planet, with original data from CSIRO and NASA.

 

For up-to-date information on temperature, carbon dioxide, and other indicators of a warming planet, see the NASA Global Climate Change - Key Indicators page.

Need more information?

See the following primers and resources for more introductory information on climate change.

Climate Change Resource Center:
FAQs

United States Global Change Research Program:
The Third National Climate Assessment

NASA Global Climate Change
Climate change: How do we know?

Center for Climate and Energy Solutions:
Climate Change – The Basics

 

References

Anderson A.; Bows, A. 2011. Beyond 'dangerous' climate change: emission scenarios for a new world. Philosophical Transactions of the Royal Society. 369: 20-44.

Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M.; Showers, W.; Hoffmann, S.; Lotti-Bond, R.; Hajdas, I.; Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science. 294: 2130-2136.

Carbon Dioxide Information Analysis Center (CDIAC). 2014. Recent Greenhouse Gas Concentrations. (Accessed 10-31-2014)

Deser, C.; Alexander, M.A.; Xie, S.P.; Phillips, A.S. 2010. Sea Surface Temperature Variability: Patterns and Mechanisms. Annual Review of Marine Science. 2: 115-143.

Global Carbon Project. 2014. Carbon budget and trends 2014. (Accessed 10-20-2014)

Hansen, J.E. 2003. Can we defuse the global warming time bomb? (Accessed 10-31-2014)

Held, I.M.; Soden, B.J. 2000. Water vapor feedback and global warming. Annual Review of Energy and the Environment. 25:441-475.

Huber, M.; Knutti, R. 2011. Anthropogenic and natural warming inferred from changes in Earth's energy balance. Nature Geoscience. Advance Online Publication.

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2011: Summary for Policymakers [pdf]. In: Intergovernmental Panel on Climate Change, Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C. B.; Barros, V.; Stocker, T.F.; Qin, D.; Dokken, D.; Ebi, K.L.; Mastrandrea, M. D.; Mach, K. J.; Plattner, G.K.; Allen, S.; Tignor, M.; Midgley, P. M. (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

Lean, J. 2010. Cycles and trends in solar irradiance and climate. Wiley Interdisciplinary Reviews: Climate Change. 1: 111-122.

Li, J.;  Xie, S.-P.;  Cook, E.R.; Morales, M.; Christie, D.; Johnson, N.; Chen, F.;  D'Arrigo, R.; Fowler, A.; Gou, X.; Fang, K. 2013. El Niño modulations over the past seven centuries. Nature Climate Change. 3:822-826.

Mann, M.E.; Zhang, Z.; Rutherford, S.; Bradley, R.S.; Hughes, M.K.; Shindell, D.; Ammann, C.; Faluvegi, G.; Ni, F. 2009. Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science. 27 (326): 1256-1260.

Mantua, N. J.; Hare, S. R.; Zhang, Y.; Wallace, J. M.; Francis, R.C. 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society 78:1069-1079.

NASA Global Climate Change. 2014. Vital Signs of the Planet. (Accessed 10-31-2014).

NASA Goddard Institute for Space Studies. 2014. NASA Finds 2013 Sustained Long-Term Climate Warming Trend. Research News. (Accessed 10-31-2014).

NASA Earth Observatory. 2000. Features: Milutin Milankovitch. (Accessed 10-31-2014).

NASA Earth Observatory. 2009. Features: El Nino, La Nina, and Rainfall. (Accessed 10-31-2014).

NOAA Earth System Research Laboratory. 2014. Mauna Loa Observatory. (Accessed 10-31-2014)

NOAA National Climatic Data Center. 2014. (Accessed 10-31-2014).

Ramanathan, V.; Feng, Y. 2009. Air pollution, greenhouse gases and climate change: Global and regional perspectives. Atmospheric Environment. 43: 37-50.

Tyndal J. 1861. On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction. Philosophical Magazine. 22:169-94, 273-85

United States Global Change Research Program (USGCRP). 2009. Global Climate Change Impacts in the United States. Karl, T.R.; Melillo, J.M.; Peterson, T.C. (eds). Cambridge University Press.

U.S. Global Change Research Program. 2014. The Third National Climate Assessment. Melillo, J.M.; Richmond, T.C.; Yohe, G.W. (eds.). 841 p.

Wanner, H.; Beer, J.; Butikofer, J.; Crowley, T.J.; Cubasch, U.; Fluckiger, J.; Goosse, H.; Grosjean, M.; Joos, F.; Kaplan, J.O.; Kuttel,M.; Muller, S.A.; Prentice, C.; Solomina, O.; Stocker, T.F.; Tarasov, P.; Wagner,M.; Widmann, M. 2008. Mid- to Late Holocene climate change: an overview. Quaternary Science Reviews. 27: 1791-1828.

Wolff, E.W. 2011. Greenhouse gases in the Earth system: a palaeoclimate perspective. Philosophical Transactions of the Royal Society. 369: 2133-2147.

Climate Mechanisms

The Greenhouse Effect

The physical mechanisms that cause greenhouse gases to warm the planet, commonly known as the greenhouse effect, are well understood and were scientifically demonstrated beginning in the mid-1800s (Tyndal 1861). Of the solar energy that is directed toward Earth, about 30% is reflected back to space by clouds, dust, and haze (Ramanathan & Feng 2009). The remaining 70% is absorbed by the atmosphere and the Earth’s surface. The Earth’s warmed surface releases some of that absorbed energy as infrared radiation, a form of light, but invisible to human eyes. Greenhouse gases in the atmosphere including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor, absorb this infrared radiation and keep it from passing into space. This energy is then reradiated in all directions, and the energy that is directed back toward the Earth warms the planet.

Figure 4

Figure 4 -An idealized model of the greenhouse effect. Source: IPCC 2007 Ch.1

Human Influence on Greenhouse Gases

The greenhouse effect is a natural process, and without greenhouse gases in the Earth’s atmosphere, the average temperature on the surface of the Earth would be would be about zero degrees Fahrenheit (IPCC 2007 Ch.1). However human activities have led directly to increases in greenhouse gas concentrations and therefore an enhanced greenhouse effect, causing warming on the Earth’s surface.

The 2007 United Nations Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) emphasized the clear link between human-caused greenhouse gases and observed climate changes. The most recent IPCC Assessment (AR5) represents the most substantive evaluation of climate change to date, and strengthens this link even further, observing  " Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely [95-100% certainty] that human influence has been the dominant cause of the observed warming since the mid-20th century.” (IPCC 2013, Summary for Policymakers).  Independent studies using a variety of methods strongly corroborate this conclusion (e.g. Lean 2010, Huber & Knutti 2011). Examinations and model simulations of many possible explanations of global warming show that we can only explain the strong temperature increases of the past 120 years if we account for human influences (Figure 5).



Figure 5

Figure 5 - Contributions of to the average monthly global surface temperatures by individual ENSO [El Niño], volcanic, solar, and human-caused influences. Source: Lean 2010

Human activity has had the most notable impact on carbon dioxide concentrations, which as noted earlier, have increased dramatically (Figure 2), mainly through fossil fuel burning, cement production, and deforestation. Methane, another potent greenhouse gas, is emitted by processes such as decomposition in wetlands, and from activities such as rice and livestock agriculture and biomass burning. Human-caused sources of methane are estimated at 50-65% of total global methane emissions for the 2000’s (IPCC 2013 Ch.6). Nitrous oxides have been increasing due in part to agricultural fertilization and fossil fuel burning; other gases emitted from industrial processes, such as halocarbons, also play a role in warming (Figure 5). Many of these greenhouse gases are likely to reside in the atmosphere for decades to centuries (CDIAC 2014). The most abundant greenhouse gas is water vapor, but water vapor is short lived in the atmosphere (on the order of days) and is dependent on temperature. So, human activities have little direct influence on water vapor, although human-caused warming can increase water vapor concentrations and amplify the warming effect (Held and Soden 2000).


Figure 6 -The amount of warming influence (red bars) or cooling influence (blue bars) that different factors have exerted on the Earth’s climate over the industrial era (from 1750 – 2011). A longer bar signifies a greater influence. Source: IPCC 2013 Ch.8

Need more information?

See the following primers and resources for more introductory information on climate change.

Climate Change Resource Center:
FAQs

United States Global Change Research Program:
The Third National Climate Assessment

NASA Global Climate Change
Climate change: How do we know?

Center for Climate and Energy Solutions:
Climate Change – The Basics

 

References

Anderson A.; Bows, A. 2011. Beyond 'dangerous' climate change: emission scenarios for a new world. Philosophical Transactions of the Royal Society. 369: 20-44.

Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M.; Showers, W.; Hoffmann, S.; Lotti-Bond, R.; Hajdas, I.; Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science. 294: 2130-2136.

Carbon Dioxide Information Analysis Center (CDIAC). 2014. Recent Greenhouse Gas Concentrations. (Accessed 10-31-2014)

Deser, C.; Alexander, M.A.; Xie, S.P.; Phillips, A.S. 2010. Sea Surface Temperature Variability: Patterns and Mechanisms. Annual Review of Marine Science. 2: 115-143.

Global Carbon Project. 2014. Carbon budget and trends 2014. (Accessed 10-20-2014)

Hansen, J.E. 2003. Can we defuse the global warming time bomb? (Accessed 10-31-2014)

Held, I.M.; Soden, B.J. 2000. Water vapor feedback and global warming. Annual Review of Energy and the Environment. 25:441-475.

Huber, M.; Knutti, R. 2011. Anthropogenic and natural warming inferred from changes in Earth's energy balance. Nature Geoscience. Advance Online Publication.

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2011: Summary for Policymakers [pdf]. In: Intergovernmental Panel on Climate Change, Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C. B.; Barros, V.; Stocker, T.F.; Qin, D.; Dokken, D.; Ebi, K.L.; Mastrandrea, M. D.; Mach, K. J.; Plattner, G.K.; Allen, S.; Tignor, M.; Midgley, P. M. (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

Lean, J. 2010. Cycles and trends in solar irradiance and climate. Wiley Interdisciplinary Reviews: Climate Change. 1: 111-122.

Li, J.;  Xie, S.-P.;  Cook, E.R.; Morales, M.; Christie, D.; Johnson, N.; Chen, F.;  D'Arrigo, R.; Fowler, A.; Gou, X.; Fang, K. 2013. El Niño modulations over the past seven centuries. Nature Climate Change. 3:822-826.

Mann, M.E.; Zhang, Z.; Rutherford, S.; Bradley, R.S.; Hughes, M.K.; Shindell, D.; Ammann, C.; Faluvegi, G.; Ni, F. 2009. Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science. 27 (326): 1256-1260.

Mantua, N. J.; Hare, S. R.; Zhang, Y.; Wallace, J. M.; Francis, R.C. 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society 78:1069-1079.

NASA Global Climate Change. 2014. Vital Signs of the Planet. (Accessed 10-31-2014).

NASA Goddard Institute for Space Studies. 2014. NASA Finds 2013 Sustained Long-Term Climate Warming Trend. Research News. (Accessed 10-31-2014).

NASA Earth Observatory. 2000. Features: Milutin Milankovitch. (Accessed 10-31-2014).

NASA Earth Observatory. 2009. Features: El Nino, La Nina, and Rainfall. (Accessed 10-31-2014).

NOAA Earth System Research Laboratory. 2014. Mauna Loa Observatory. (Accessed 10-31-2014)

NOAA National Climatic Data Center. 2014. (Accessed 10-31-2014).

Ramanathan, V.; Feng, Y. 2009. Air pollution, greenhouse gases and climate change: Global and regional perspectives. Atmospheric Environment. 43: 37-50.

Tyndal J. 1861. On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction. Philosophical Magazine. 22:169-94, 273-85

United States Global Change Research Program (USGCRP). 2009. Global Climate Change Impacts in the United States. Karl, T.R.; Melillo, J.M.; Peterson, T.C. (eds). Cambridge University Press.

U.S. Global Change Research Program. 2014. The Third National Climate Assessment. Melillo, J.M.; Richmond, T.C.; Yohe, G.W. (eds.). 841 p.

Wanner, H.; Beer, J.; Butikofer, J.; Crowley, T.J.; Cubasch, U.; Fluckiger, J.; Goosse, H.; Grosjean, M.; Joos, F.; Kaplan, J.O.; Kuttel,M.; Muller, S.A.; Prentice, C.; Solomina, O.; Stocker, T.F.; Tarasov, P.; Wagner,M.; Widmann, M. 2008. Mid- to Late Holocene climate change: an overview. Quaternary Science Reviews. 27: 1791-1828.

Wolff, E.W. 2011. Greenhouse gases in the Earth system: a palaeoclimate perspective. Philosophical Transactions of the Royal Society. 369: 2133-2147.

Natural Climate Cycles

Climate varies without human influence, and this natural variation is a backdrop for the human-caused climate change occurring now. These patterns hold important lessons for understanding the magnitude and scope of current and future climate changes.

Cyclical variations in the Earth’s climate occur at multiple time scales, from years to decades, centuries, and millennia. Cycles at each scale are caused by a variety of physical mechanisms. Climate over any given period is an expression of all of these nested mechanisms and cycles operating together.

Millennial Climate Cycles

Major glacial (cold) and interglacial (warm) periods are initiated by changes in the Earth’s orbit around the Sun, called Milankovitch cycles. These cycles have occurred at different intensities on multi-millennial time scales (10,000 – 100,000 year periods). The orbital changes occur slowly over time, influencing where solar radiation is received on the Earth’s surface during different seasons (NASA 2000).

By themselves, these changes in the distribution of solar radiation are not strong enough to cause large temperature changes. However they can initiate powerful feedback mechanisms that amplify the slight warming or cooling effect caused by the Milankovitch cycle. One of these feedbacks is caused through changes in global surface reflectivity (also called albedo). Even a slight increase in solar radiation at northern latitudes can increase ice melt. As a result of ice loss, less sunlight is reflected from the bright white surface of the ice, and more is absorbed by the Earth, increasing overall warming. A second feedback mechanism involves atmospheric greenhouse gas concentrations, such as carbon dioxide. The slight warming initiated by changes to Earth’s orbit warms oceans, which allows them to release carbon dioxide. As we’ve seen, more carbon dioxide in the atmosphere causes more warming, creating an amplifying effect (Hansen 2003). Distinct feedbacks in atmospheric CO2 concentrations may lag warming or cooling caused by orbital changes by as much as 1000 years.

In this way, what begins as fairly minor changes in orbit can produce the glacial and interglacial cycles of the last 800,000 years. A major concern with current climate change is that similar feedback mechanisms will cause a ‘runaway’ warming effect in modern times that will be extremely difficult to halt or reverse.

Century-scale Climate Cycles

In addition to multi-millennial glacial and interglacial cycles, there are shorter cold-warm cycles that occur on approximately 200 to 1,500 year time scales. The mechanisms that cause these cycles are not completely understood, but are thought to be driven by changes in the sun, along with several corresponding changes such as ocean circulation patterns (Bond et al. 2001, Wanner et al. 2008). The Medieval Warm Period (900-1300 AD) and the Little Ice Age (1450 to 1900 AD) are examples of warm and cold phases in one of these cycles. Some of these cycles, such as the Medieval Warm Period, may be regional, not necessarily reflecting large changes in global averages. Understanding and reconstructing the regional patterns of climate change during each of these periods is considered very important in accurately analyzing future regional impacts such as drought patterns (Mann et al. 2009).

Interannual to Decadal Climate Cycles

Ocean-atmosphere interactions regularly cause climate cycles on the order of years to decades. One of the most well-known cycles is the El Niño-Southern Oscillation (ENSO), an interaction between ocean temperatures and atmospheric patterns (commonly known as El Niño or its opposite effect, La Niña). ENSO events occur every 3 to 7 years, and bring different conditions to different parts of the world (NASA 2009). For example, in the U.S., El Niño events can result in a flow of warm dry air into the Northwest, but above average rainfall  in the southeast (NASA 2009).

Many other cyclical changes due to oceanic and/or atmospheric processes have been described, such as the Pacific Decadal Oscillation (PDO) which occurs in cycles of 25-45 years (Mantua et al. 1997), and the Atlantic Multi-decadal Oscillation (AMO), occurring on approximately 65-85 year cycles (Deser et al. 2010). Scientistis are studying how each of these reoccurring cycles might interact with the enhanced greenhouse effect. There is some evidence that global warming may be intensifying ENSO events (Li et al. 2013).

Implications

For more information about natural climate cycles and their implications, see a presentation by paleoecologist Connie Millar.

Natural climate cycles can help to understand what climate patterns are expected, and how the recent increase in greenhouse gas emissions is causing deviations from these expected patterns. They can offer insight into amplifying effects that may intensify warming as greenhouse gas concentrations rise (Wolff 2011). They may also provide insight on regional impacts of climate change, which will be veryimportant for developing adaptation strategies for human and ecological communities. However, it is important to recognize that current rates of global climate change are extremely rapid compared to past changes (IPCC 2013 Ch.5), and may produce conditions that have not been anticipated.

Need more information?

See the following primers and resources for more introductory information on climate change.

Climate Change Resource Center:
FAQs

United States Global Change Research Program:
The Third National Climate Assessment

NASA Global Climate Change
Climate change: How do we know?

Center for Climate and Energy Solutions:
Climate Change – The Basics

 

References

Anderson A.; Bows, A. 2011. Beyond 'dangerous' climate change: emission scenarios for a new world. Philosophical Transactions of the Royal Society. 369: 20-44.

Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M.; Showers, W.; Hoffmann, S.; Lotti-Bond, R.; Hajdas, I.; Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science. 294: 2130-2136.

Carbon Dioxide Information Analysis Center (CDIAC). 2014. Recent Greenhouse Gas Concentrations. (Accessed 10-31-2014)

Deser, C.; Alexander, M.A.; Xie, S.P.; Phillips, A.S. 2010. Sea Surface Temperature Variability: Patterns and Mechanisms. Annual Review of Marine Science. 2: 115-143.

Global Carbon Project. 2014. Carbon budget and trends 2014. (Accessed 10-20-2014)

Hansen, J.E. 2003. Can we defuse the global warming time bomb? (Accessed 10-31-2014)

Held, I.M.; Soden, B.J. 2000. Water vapor feedback and global warming. Annual Review of Energy and the Environment. 25:441-475.

Huber, M.; Knutti, R. 2011. Anthropogenic and natural warming inferred from changes in Earth's energy balance. Nature Geoscience. Advance Online Publication.

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2011: Summary for Policymakers [pdf]. In: Intergovernmental Panel on Climate Change, Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C. B.; Barros, V.; Stocker, T.F.; Qin, D.; Dokken, D.; Ebi, K.L.; Mastrandrea, M. D.; Mach, K. J.; Plattner, G.K.; Allen, S.; Tignor, M.; Midgley, P. M. (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

Lean, J. 2010. Cycles and trends in solar irradiance and climate. Wiley Interdisciplinary Reviews: Climate Change. 1: 111-122.

Li, J.;  Xie, S.-P.;  Cook, E.R.; Morales, M.; Christie, D.; Johnson, N.; Chen, F.;  D'Arrigo, R.; Fowler, A.; Gou, X.; Fang, K. 2013. El Niño modulations over the past seven centuries. Nature Climate Change. 3:822-826.

Mann, M.E.; Zhang, Z.; Rutherford, S.; Bradley, R.S.; Hughes, M.K.; Shindell, D.; Ammann, C.; Faluvegi, G.; Ni, F. 2009. Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science. 27 (326): 1256-1260.

Mantua, N. J.; Hare, S. R.; Zhang, Y.; Wallace, J. M.; Francis, R.C. 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society 78:1069-1079.

NASA Global Climate Change. 2014. Vital Signs of the Planet. (Accessed 10-31-2014).

NASA Goddard Institute for Space Studies. 2014. NASA Finds 2013 Sustained Long-Term Climate Warming Trend. Research News. (Accessed 10-31-2014).

NASA Earth Observatory. 2000. Features: Milutin Milankovitch. (Accessed 10-31-2014).

NASA Earth Observatory. 2009. Features: El Nino, La Nina, and Rainfall. (Accessed 10-31-2014).

NOAA Earth System Research Laboratory. 2014. Mauna Loa Observatory. (Accessed 10-31-2014)

NOAA National Climatic Data Center. 2014. (Accessed 10-31-2014).

Ramanathan, V.; Feng, Y. 2009. Air pollution, greenhouse gases and climate change: Global and regional perspectives. Atmospheric Environment. 43: 37-50.

Tyndal J. 1861. On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction. Philosophical Magazine. 22:169-94, 273-85

United States Global Change Research Program (USGCRP). 2009. Global Climate Change Impacts in the United States. Karl, T.R.; Melillo, J.M.; Peterson, T.C. (eds). Cambridge University Press.

U.S. Global Change Research Program. 2014. The Third National Climate Assessment. Melillo, J.M.; Richmond, T.C.; Yohe, G.W. (eds.). 841 p.

Wanner, H.; Beer, J.; Butikofer, J.; Crowley, T.J.; Cubasch, U.; Fluckiger, J.; Goosse, H.; Grosjean, M.; Joos, F.; Kaplan, J.O.; Kuttel,M.; Muller, S.A.; Prentice, C.; Solomina, O.; Stocker, T.F.; Tarasov, P.; Wagner,M.; Widmann, M. 2008. Mid- to Late Holocene climate change: an overview. Quaternary Science Reviews. 27: 1791-1828.

Wolff, E.W. 2011. Greenhouse gases in the Earth system: a palaeoclimate perspective. Philosophical Transactions of the Royal Society. 369: 2133-2147.

Expected Effects in the U.S.

Temperature and Precipitation Projections

Global average temperatures are projected to rise over this century and beyond, causing continued changes in all components of the climate system. Temperature increases will vary regionally and seasonally; for example, temperature increases at polar latitudes are expected to be greater than increases near the equator (USGCRP 2014 Ch. 2). Part of this future warming is inevitable due to the long-lived greenhouse gases that are already present in Earth’s atmosphere. However the full extent of warming will depend in part on future emissions of greenhouse gases. The IPCC has developed  four ‘representative concentration pathways’, or RCP’s, that describe a plausible range of future emissions. To develop these RCP’s, scientists selected different levels of greenhouse gas concentrations for the year 2100 that are each possible given current scientific knowledge. Each pathway could be achieved by different socioeconomic scenarios, including future trajectories  of population, economic and technological change, and political choices  (IPCC 2013, Summary for Policy Makers). Having these RCP’s provides a way for  climate modelers to compare projected future climates using consistent sets of assumptions about future levels of emissions.  

By 2100, average temperatures in the U.S. are expected to increase by approximately 8°F or more (4.4°C) under a high RCP with similar rates to current greenhouse gas emissions and by approximately 2.5°F (1.4°C) under a  lower RCP that assumes immediate and rapid greenhouse gas reductions (USGCRP 2014 Ch. 2 – Figure 7). Both lower and higher temperature changes are possible, if future emissions fall below or above these pathways.


Figure 7 - Projected average temperature changes in the U.S. for 2071-2099, relative to the period from 1970-1999. The wide range in projections is due to the different pathways (RCP’s) that are considered. Source: USGCRP 2014 Ch. 2. -Third National Climate Change Assessment

Precipitation changes will also vary seasonally and regionally, and are more uncertain than temperature changes. Models project that northern areas in the U.S. will generally become wetter, and southern areas will generally become drier, especially the Southwest (USGCRP 2014 Ch. 2). In northern areas, a greater proportion of annual precipitation is expected in the winter and spring, and may fall as rain rather than snow due to warmer temperatures. In the Southwest,drier conditions are projected particularly for the winter and spring (USGCRP 2014 Ch. 2). Across all areas of the United States, the number of heavy precipitation has increased since the 1950’s, and is expected to increase further over the next century (Figure 8). Although modeled precipitation projections are improving and projected trends have remained consistent since the last IPCC report in 2007, there is still a high degree of uncertainty and specific regional patterns could differ from these general trends.


Figure 8 - Projected changes in the frequency of extreme daily precipitation events for 2081-2100, compared to 1981-2000. An extreme event is a daily amount of precipitation that now occurs once every 20 years. Under a low emissions pathway (RCP 2.6) these events would occur twice as often, under a high emissions pathway (RCP 8.5) events would occur as much as five times as often.Source: USGCRP 2014 Ch. 2. -Third National Climate Change Assessment

Effects on Ecosystems and Ecosystem Processes

For overviews on regional climate change projections in the U.S. please see the USGCRP report: Alaska, Coasts, Great Plains, Hawaii and Pacific Islands, Midwest, Northeast, Northwest, Southeast, Southwest

The climate changes expected over the next century will have huge consequences for ecosystems and the benefits they provide, including the provision of wood and fuel, food, temperature and flood regulation, erosion control, recreational and aesthetic value, and species habitat, among others.

Climate changes are likely to affect important ecological processes that will in turn affect key natural resources. For example, temperature and precipitation changes have strong implications for water resources and hydrologic cycling. In addition, disturbances such as insects, wildfire, invasive plants, and forest diseases will become more frequent in some areas of the country. The emissions that cause climate change  also generate air pollution that can affect forest growth and health.

Coupled with altered hydrology and increased disturbance and stress, climate change will affect how species are distributed within the U.S., and will cause changes for aquatic ecosystems, wildlife species and soils. How these resources are affected will have broad implications for maintaining ecosystem services, including biodiversity and the carbon storage capabilities of forests. Each impact on one aspect of an ecosystem can affect a variety of others, producing a series of cumulative effects that can make it difficult for ecosystems to adapt.

Meeting the diverse challenges that climate change presents for Earth's environments requires many approaches, and specific responses will depend heavily on the management goals for a particular resource see more at Managing Lands Under Climate Change. Scientists are currently working to understand the challenges posed to ecosystems by examining characteristics and changes in landscapes, modeling responses to climate change, and conducting assessments on impacts and ecosystem vulnerabilities Public lands, private lands, wilderness areas, and urban neighborhoods will all be affected, and each will require different management considerations. Specific management practices such as silviculture are potentially valuable tools for helping forests respond to a changing climate.

For those charged with managing ecosystems, climate change can seem like a daunting challenge. Fortunately, a range of management options exist to help ecosystems adapt to climate changes, and to contribute to climate change mitigation by reducing the amount of greenhouse gases in the atmosphere. These options are often complementary to actions that land managers employ regularly.

The majority of the CCRC is dedicated describing ecosystem responses to climate change, and how natural resource management may be able to respond to those changes. Please follow the links in the text, or explore the rest of the website for further information.

Need more information?

See the following primers and resources for more introductory information on climate change.

Climate Change Resource Center:
FAQs

United States Global Change Research Program:
The Third National Climate Assessment

NASA Global Climate Change
Climate change: How do we know?

Center for Climate and Energy Solutions:
Climate Change – The Basics

 

References

Anderson A.; Bows, A. 2011. Beyond 'dangerous' climate change: emission scenarios for a new world. Philosophical Transactions of the Royal Society. 369: 20-44.

Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M.; Showers, W.; Hoffmann, S.; Lotti-Bond, R.; Hajdas, I.; Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science. 294: 2130-2136.

Carbon Dioxide Information Analysis Center (CDIAC). 2014. Recent Greenhouse Gas Concentrations. (Accessed 10-31-2014)

Deser, C.; Alexander, M.A.; Xie, S.P.; Phillips, A.S. 2010. Sea Surface Temperature Variability: Patterns and Mechanisms. Annual Review of Marine Science. 2: 115-143.

Global Carbon Project. 2014. Carbon budget and trends 2014. (Accessed 10-20-2014)

Hansen, J.E. 2003. Can we defuse the global warming time bomb? (Accessed 10-31-2014)

Held, I.M.; Soden, B.J. 2000. Water vapor feedback and global warming. Annual Review of Energy and the Environment. 25:441-475.

Huber, M.; Knutti, R. 2011. Anthropogenic and natural warming inferred from changes in Earth's energy balance. Nature Geoscience. Advance Online Publication.

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2011: Summary for Policymakers [pdf]. In: Intergovernmental Panel on Climate Change, Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C. B.; Barros, V.; Stocker, T.F.; Qin, D.; Dokken, D.; Ebi, K.L.; Mastrandrea, M. D.; Mach, K. J.; Plattner, G.K.; Allen, S.; Tignor, M.; Midgley, P. M. (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

Lean, J. 2010. Cycles and trends in solar irradiance and climate. Wiley Interdisciplinary Reviews: Climate Change. 1: 111-122.

Li, J.;  Xie, S.-P.;  Cook, E.R.; Morales, M.; Christie, D.; Johnson, N.; Chen, F.;  D'Arrigo, R.; Fowler, A.; Gou, X.; Fang, K. 2013. El Niño modulations over the past seven centuries. Nature Climate Change. 3:822-826.

Mann, M.E.; Zhang, Z.; Rutherford, S.; Bradley, R.S.; Hughes, M.K.; Shindell, D.; Ammann, C.; Faluvegi, G.; Ni, F. 2009. Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science. 27 (326): 1256-1260.

Mantua, N. J.; Hare, S. R.; Zhang, Y.; Wallace, J. M.; Francis, R.C. 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society 78:1069-1079.

NASA Global Climate Change. 2014. Vital Signs of the Planet. (Accessed 10-31-2014).

NASA Goddard Institute for Space Studies. 2014. NASA Finds 2013 Sustained Long-Term Climate Warming Trend. Research News. (Accessed 10-31-2014).

NASA Earth Observatory. 2000. Features: Milutin Milankovitch. (Accessed 10-31-2014).

NASA Earth Observatory. 2009. Features: El Nino, La Nina, and Rainfall. (Accessed 10-31-2014).

NOAA Earth System Research Laboratory. 2014. Mauna Loa Observatory. (Accessed 10-31-2014)

NOAA National Climatic Data Center. 2014. (Accessed 10-31-2014).

Ramanathan, V.; Feng, Y. 2009. Air pollution, greenhouse gases and climate change: Global and regional perspectives. Atmospheric Environment. 43: 37-50.

Tyndal J. 1861. On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction. Philosophical Magazine. 22:169-94, 273-85

United States Global Change Research Program (USGCRP). 2009. Global Climate Change Impacts in the United States. Karl, T.R.; Melillo, J.M.; Peterson, T.C. (eds). Cambridge University Press.

U.S. Global Change Research Program. 2014. The Third National Climate Assessment. Melillo, J.M.; Richmond, T.C.; Yohe, G.W. (eds.). 841 p.

Wanner, H.; Beer, J.; Butikofer, J.; Crowley, T.J.; Cubasch, U.; Fluckiger, J.; Goosse, H.; Grosjean, M.; Joos, F.; Kaplan, J.O.; Kuttel,M.; Muller, S.A.; Prentice, C.; Solomina, O.; Stocker, T.F.; Tarasov, P.; Wagner,M.; Widmann, M. 2008. Mid- to Late Holocene climate change: an overview. Quaternary Science Reviews. 27: 1791-1828.

Wolff, E.W. 2011. Greenhouse gases in the Earth system: a palaeoclimate perspective. Philosophical Transactions of the Royal Society. 369: 2133-2147.

Was this page helpful?

Please help us improve the CCRC by giving us feedback.