What is global warming?
What causes global warming?
Is Global Warming Happening?
If Global Warming Is Happening, Why Did Colorado Have Such High Snowfall in 2007/2008?
What are the Potential Impacts of Global Warming?
What Steps Have Been Suggested to Reduce the Impact of Global Warming?
What are Governments and Other Nations Doing to Reduce Greenhouse Gas Emissions?
What Has the United States Done to Combat Global Warming?
What Can I Do?

What is Global Warming?
The phrase global warming refers to the documented historical warming of the Earth's surface based on worldwide temperature records that have been maintained since the 1880s. The term global warming is often used synonymously with the term climate change, but the two terms have distinct meanings. 

• Global warming is the combined result of human-caused emissions of greenhouse gases and to a much lesser extent, changes in solar irradiance (the amount of sunlight striking the Earth each year).
• Climate change refers to changes caused by global warming in weather (temperatures, precipitation, frequency of heat waves, etc.) and other climate system components, such as Arctic sea ice extent.[1]

What Causes Global Warming?
The burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.

Greenhouse gases are necessary to life as we know it, because they keep the planet's surface warmer than it otherwise would be. But, as the concentrations of these gases continue to increase in the atmosphere, the Earth's temperature is climbing above past levels.[2]

There are four major types of greenhouse gases that contribute to global warming:

Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle.

Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.

Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases ("High GWP gases").[3]

Worldwide, carbon dioxide makes up 74% of total annual greenhouse gas emissions.   Methane accounts for 16% of total emissions, nitrous oxide 9%, and fluorinated gases (high global warming potential gases) account for 1% of emissions.[4]  In the United States, carbon dioxide accounts for 84.8% of all global warming gas emissions.  The largest sources of U.S. carbon dioxide emissions include electricity generation (for industrial, commercial, and residential uses) and combustion of fossil fuels for transportation. [5]

Is Global Warming Happening?
Yes.  There is overwhelming consensus among the world's leading climate scientists that the evidence that global warming is happening is "unequivocal" and that the phenomenon is "very likely" caused by emissions of greenhouse gases generated by human activity.[6] According to National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) data, the Earth's average surface temperature has increased by about 1.2 to 1.4ºF in the last 100 years. The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the warming in recent decades is very likely the result of human activities.  Other aspects of the climate are also changing, such as rainfall patterns, snow and ice cover, and sea level.[7]

If Global Warming Is Happening, Why Did Colorado Have Such High Snowfall in 2007/2008?
According to climate scientists and meteorologists, global warming will cause increasing unpredictability in year-to-year climatic conditions, but on average, over time, the most likely impacts on Colorado's climate are expected to be:

• Warmer average temperatures;
• Increased precipitation falling as rain instead of snow in some areas; and
• Increased drought in some areas, resulting in an increase in wildfires.[8]

What are the Potential Impacts of Global Warming?
The impacts of global warming will depend on a variety of factors, most importantly the concentration of greenhouse gases in the atmosphere. 

The National Oceanic and Atmospheric Administration (NOAA) and NASA have determined that the Earth's average surface temperature has already increased by about 1.2 to 1.4ºF in the last 100 years.[9]  This increase in temperature has already led to an observed rise in sea levels (of several millimeters per year), decreases in arctic sea ice, and mountain snow and glacier cover.  Precipitation has increased in areas of North and South America and in northern Europe and northern and central Asia.  Precipitation has decreased in Africa's Sahel, the Mediterranean, southern Africa and southern Asia.  Across the globe, more areas have been affected by drought.  Cold days, cold nights, and frosts have become less frequent, and hot days and nights have become more frequent.  The intensity of tropical cyclones has also increased in the North Atlantic Ocean.[10]

If greenhouse gas emissions continue to increase, climate models predict that the average temperature at the Earth's surface could increase from 3.2 to 7.2ºF above 1990 levels by the end of this century.[11]

In Colorado, the impacts of temperature increases in this range are likely to cause:[12]

• Decreased snowpack, more winter flooding, and reduced summer stream and river flows, decreasing water availability and increasing drought, exacerbating competition for over-allocated water resources;
• In the early decades of the century, moderate climate change is projected to increase aggregate yields of rain-fed agriculture by 5 to 20%, but with important variability among regions.  Major challenges are projected for crops that are near the warm end of their suitable range or which depend on highly utilized water resources.  Higher temperatures are expected to decrease corn and wheat production.
• Cities that currently experience heat waves are expected to be further challenged by an increased number, intensity, and duration of heat waves during the course of the century, with potential for adverse health impacts;
• Increasing species range shifts and risk of species extinction; and,
• Increasing wildfire risk. The total amount of forests in Colorado could decline by 30% and insect populations may thrive as temperatures increase, killing trees.[13]

Worldwide, scientists project a variety of probable impacts due to increases of temperature increases of 3.2 to 7.2ºF above 1990 levels:[14]

Africa

• By 2020, between 75 and 250 million people are projected to be exposed to increased water stress due to climate change.
• By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%.  Agricultural production, including access to food, in many African countries is projected to be severely compromised.  This would further adversely affect food security and exacerbate malnutrition.
• Towards the end of the 21st century, projected sea level rise will affect low-lying coastal areas with large populations. The cost of adaptation could amount to at least 5 to 10% of Gross Domestic Product (GDP).
• By 2080, an increase of 5 to 8% of arid and semi-arid land in Africa is projected under a range of climate scenarios (TS).

Asia

• By the 2050s, freshwater availability in Central, South, East, and South-East Asia, particularly in large river basins, is projected to decrease.
• Coastal areas, especially heavily populated mega-delta regions in South, East, and South-East Asia, will be at greatest risk due to increased flooding from the sea and, in some mega-deltas, flooding from rivers.
• Climate change is projected to compound the pressures on natural resources and the environment associated with rapid urbanization, industrialization, and economic development.
• Endemic morbidity and mortality due to diarrhoeal disease, primarily associated with floods and droughts, are expected to rise in East, South, and South-East Asia due to projected changes in the hydrological cycle.

Australia and New Zealand

• By 2020, significant loss of biodiversity is projected to occur in some ecologically rich sites, including the Great Barrier Reef and Queensland Wet Tropics.
• By 2030, water security problems are projected to intensify in New Zealand, in southern and eastern Australia, in Northland, and in some eastern regions.
• By 2030, production from agriculture and forestry is projected to decline over much of southern and eastern Australia, and over parts of eastern New Zealand, due to increased drought and fire.  However, in New Zealand, initial benefits are projected in some other regions.
• By 2050, ongoing coastal development and population growth in some areas of Australia and New Zealand are projected to exacerbate risks from sea level rise and increases in the severity and frequency of storms and coastal flooding.

Europe

• Climate change is expected to magnify regional differences in Europe's natural resources and assets.
• Negative impacts will include increased risk of inland flash floods and more frequent coastal flooding and increased erosion (due to storminess and sea level rise).
• Mountainous areas will face glacier retreat, reduced snow cover and winter tourism, and extensive species losses (in some areas up to 60% under high emissions scenarios by 2080).
• In southern Europe, climate change is projected to worsen conditions (high temperatures and drought) in a region already vulnerable to climate variability, and to reduce water availability, hydropower potential, summer tourism and, in general, crop productivity.
• Climate change is also projected to increase the health risks due to heat waves and the frequency of wildfires.

Latin America

• By mid-century, increases in temperature and associated decreases in soil water are projected to lead to gradual replacement of tropical forest by savanna in eastern Amazonia.  Semi-arid vegetation will tend to be replaced by arid-land vegetation.
• There is a risk of significant biodiversity loss through species extinction in many areas of tropical Latin America.
• Productivity of some important crops is projected to decrease and livestock productivity to decline, with adverse consequences for food security.
• In temperate zones, soybean yields are projected to increase.
• Overall, the number of people at risk of hunger is projected to increase (TS; medium confidence).[sg1] 
• Changes in precipitation patterns and the disappearance of glaciers are projected to significantly affect water availability for human consumption, agriculture, and energy generation.

North America

• Warming in western mountains is projected to cause decreased snowpack, more winter flooding, and reduced summer flows, exacerbating competition for over-allocated water resources.
• In the early decades of the century, moderate climate change is projected to increase aggregate yields of rain-fed agriculture by 5 to 20%, but with important variability among regions.
• Major challenges are projected for crops that are near the warm end of their suitable range or which depend on highly utilized water resources.
• Cities that currently experience heat waves are expected to be further challenged by an increased number, intensity, and duration of heat waves during the course of the century, with potential for adverse health impacts.
• Coastal communities and habitats will be increasingly stressed by climate change impacts interacting with development and pollution.

Polar Regions

• The main projected biophysical effects are reductions in thickness and extent of glaciers, ice sheets, and sea ice, and changes in natural ecosystems with detrimental effects on many organisms, including migratory birds, mammals and higher predators.
• For human communities in the Arctic, impacts are projected to be mixed, particularly those resulting from changing snow and ice conditions.
• Detrimental impacts would include those on infrastructure and traditional indigenous ways of life.
• In both polar regions, specific ecosystems and habitats are projected to be vulnerable, as climatic barriers to species invasions are lowered.

Small Islands

• Sea level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening vital infrastructure, settlements, and facilities that support the livelihood of island communities.
• Deterioration in coastal conditions, such as erosion of beaches and coral bleaching, is expected to affect local resources.
• By mid-century, climate change is expected to reduce water resources in many small islands, e.g. in the Caribbean and Pacific, to the point where they become insufficient to meet demand during low-rainfall periods.
• With higher temperatures, increased invasion by non-native species is expected to occur, particularly on mid- and high-latitude islands.

What Steps Have Been Suggested to Reduce the Impact of Global Warming?
The Kyoto Protocol called for industrialized countries to reduce their combined emissions of six major greenhouse gases during the five-year period from 2008 to 2012 to below 1990 levels.[15] There is strong consensus among the scientific and policy communities that these targets (which are unlikely to be met) represented an important first step in catalyzing the international effort to reduce global greenhouse gas emissions.  However, scientists now suggest that the reductions proposed by the Kyoto Protocol are inadequate and have called for more substantial reductions of 20% of greenhouse gas emissions by 2020 and 80% or more of greenhouse gas emissions by 2050.  The United Nations Intergovernmental Panel on Climate Change (IPCC) said temperature increases that began more than a century ago could be capped at 3.6 degrees (F) if nations level greenhouse gas emissions in the next decade and then reduce them between 50 percent and 85 percent by 2050.[16]

To achieve these objectives, scientists have called for improved energy efficiency, expanded use of renewable energy, and better agricultural and forestry practices.  The panel also said more countries could enact penalties for emitting carbon dioxide, the chief global warming gas.  Additionally, the IPCC called on countries to end subsidies for fossil fuels, require fuel economy standards for all cars, update building energy codes, use fertilizer and irrigation more efficiently on farms, and stop deforestation.[17]

What are Governments and Other Nations Doing to Reduce Greenhouse Gas Emissions?
One hundred and seventy-three nations have ratified the Kyoto Protocol, a 1997 international agreement that seeks to reduce emissions of greenhouse gases.  California, Hawaii, and New Jersey have mandatory greenhouse gas reduction laws and at least 11 other states have set reduction targets, including Colorado.[18]  The European Union has committed to reducing its overall emissions to at least 20% below 1990 levels by 2020, and is ready to scale up this reduction to as much as 30% under a new global climate change agreement if other developed countries make comparable efforts.  It has also set itself the target of increasing the share of renewables in energy use to 20% by 2020.[19]

What Has the United States Done to Combat Global Warming?
The United States has not taken aggressive action to combat global warming and has not ratified the Kyoto Protocol agreement.  To date, U.S. actions to reduce emissions of global warming gases have relied on voluntary action from impacted sources of emissions.[20] [sg2]  U.S. emissions of global warming gases increased 15.8 percent between 1990 and 2004.[21] The United States now accounts for roughly a quarter of all humanmade greenhouse gases released into the atmosphere worldwide.  On April 16, 2008, President Bush announced new goals on climate change.  However, the President's proposal not only fails to limit current emissions of greenhouse gases, but also fails to even reduce the growth in greenhouse gas emissions until 2025.[22]

What Can I Do?
Send an email to Senator Ken Salazar today asking him to take aggressive action to reduce global warming emissions.

» Take Action Today

While no single act of Congress can immediately reduce emissions enough to ensure that we don't experience any increase in global temperatures, passage of the Climate Security would represent an important first step, resulting in reductions of global warming gases by 63% by 2050. In order to meet the task of reducing our emissions enough to head off the most serious impacts of global warming we must act now.

[1] Stephen (Lead Author); Kevin Vranes (Topic Editor). 2008. "Global warming." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth March 14, 2007; Last revised January 3, 2008; Retrieved May 7, 2008.

[2] U.S. Environmental Protection Agency.  Last updated on Tuesday, April 1st, 2008.  Retrieved May 7, 2008

[3] U.S. Environmental Protection Agency (EPA), Retrieved May 6, 2008

[4] U.S. Environmental Protection Agency, retrieved May 6, 2008

[5] U.S. Environmental Protection Agency, retrieved May 6, 2008

[6] IPCC 2007: Synthesis Report, Summary for Policymakers, Intergovernmental Panel on Climate Change, Bernstein, Lenny et. Al., World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), November 2007.  Retrieved May 7, 2008

[7] U.S. Environmental Protection Agency.  Last updated on Tuesday, April 1st, 2008.  Retrieved May 7, 2008

[8] IPCC 2007: Synthesis Report, Summary for Policymakers, Intergovernmental Panel on Climate Change, Bernstein, Lenny et. Al., World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), November 2007.  Retrieved May 7, 2008

[9] U.S. Environmental Protection Agency.  Last updated on Tuesday, April 1st, 2008.  Retrieved May 7, 2008 at:

[10] IPCC 2007: Synthesis Report, Summary for Policymakers, Intergovernmental Panel on Climate Change, Bernstein, Lenny et. Al., World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), November 2007.  Retrieved May 7, 2008

[11] U.S. Environmental Protection Agency.  Last updated on Tuesday, April 1st, 2008.  Retrieved May 7, 2008

[12] IPCC 2007: Synthesis Report, Summary for Policymakers, Intergovernmental Panel on Climate Change, Bernstein, Lenny et. Al., World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), November 2007.  Retrieved May 7, 2008

[13] U.S. Environmental Protection Agency, Office of Policy, Planning and Evaluation, Climate Change and Colorado, September 1997.

[14] IPCC 2007: Synthesis Report, Summary for Policymakers, Intergovernmental Panel on Climate Change, Bernstein, Lenny et. Al., World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), November 2007. Working Group II, Table SPM II, Retrieved May 7, 2008

[15] United Nations Environment Program.  Retrieved May 9, 2008

[16] Daley, Beth.  UN Panel Urges Greenhouse Gas Reductions Now, The Boston Globe.  May 5, 2007.  Retrieved May 9, 2008

[17] IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Retrieved May 9, 2008

[18] CDM.  Retrieved May 9, 2008

[19] European Commission, Environment Program. Last updated on April 30, 2008.  Retrieved May 9, 2008

[20] U.S. Environmental Protection Agency.  Last updated on Tuesday, April 1st, 2008.  Retrieved May 9, 2008

[21] U.S. Environmental Protection Agency.  Last updated on Tuesday, October 9, 2006.  Retrieved May 9, 2008

[22] Stolberg, Sheryl Gay, Bush Sets Greenhouse Gas Emissions Goal.  The New York Times, April 17, 2008.  Retrieved May 9, 2008