Global warming

Global Warming Causes

Global warming is primarily a problem of too much carbon dioxide (CO2) in the atmosphere—which acts as a blanket, trapping heat and warming the planet. As we burn fossil fuels like coal, oil and natural gas for energy or cut down and burn forests to create pastures and plantations, carbon accumulates and overloads our atmosphere. Certain waste management and agricultural practices aggravate the problem by releasing other potent global warming gases, such as methane and nitrous oxide. See the pie chart for a breakdown of heat-trapping global warming emissions by economic sector.

Global Warming Is Urgent and Can Be Addressed

CO2 survives in the atmosphere for a long time—up to many centuries—so its heat-trapping effects are compounded over time. Of the many heat-trapping gases, CO2 puts us at the greatest risk of irreversible changes if it continues to accumulate unabated in the atmosphere—as it is likely to do if the global economy remains dependent on fossil fuels for its energy needs. To put this in perspective, the carbon we put in the atmosphere today will literally determine not only our climate future but that of future generations as well.

Substantial scientific evidence indicates that an increase in the global average temperature of more than 3.6 degrees Fahrenheit (°F) (or 2 degrees Celsius [°C]) above pre-industrial levels poses severe risks to natural systems and to human health and well-being. The good news is that, because we as humans caused global warming, we can also do something about it. To avoid this level of warming, large emitters such as the United States need to greatly reduce heat-trapping gas emissions by mid century. Delay in taking such action means the prospect of much steeper cuts later if there is any hope of staying below the 3.6°F (2°C) temperature goal. Delayed action is also likely to make it more difficult and costly to not only make these reductions, but also address the climate consequences that occur in the meantime.

The Consequences of a Warming World

Over the last century, global average temperature has increased by more than 1°F (0.7°C). The 2001-2010 decade is the warmest since 1880—the earliest year for which comprehensive global temperature records were available. In fact, nine of the warmest years on record have occurred in just the last 10 years. This warming has been accompanied by a decrease in very cold days and nights and an increase in extremely hot days and warm nights. The continental United States, for example, has seen record daily highs twice as often as record daily lows from 2000 to 2009. While the record shows that some parts of the world are warming faster than others, the long-term global upward trend is unambiguous.

Of course, land and ocean temperature is only one way to measure the effects of climate change. A warming world also has the potential to change rainfall and snow patterns, increase droughts and severe storms, reduce lake ice cover, melt glaciers, increase sea levels, and change plant and animal behavior.

Regional Actions Add Up to Global Solutions

We encourage you to visit the solutions section of this web feature to find out how you can take action to slow the pace of climate change and help minimize the harmful consequences described in the hot spots!

Any action to reduce or eliminate the release of heat-trapping gases to the atmosphere helps slow the rate of warming and, likely, the pace and severity of change at any given hot spot. Local sources of carbon emissions vary from region to region, suggesting that solutions are often decided at the community level. The Climate Hot Map points to regional examples of climate-friendly energy, transportation, or adaptation choices. Some regions, however, must rely upon global solutions such as international agreements to reduce the carbon overload in the atmosphere that threatens them. Small islands, for example, are a paltry source of carbon emissions and yet are disproportionately affected by the consequences of global carbon overload as accelerated sea level rise threatens the very existence of low-lying islands.

Individual, regional, and national actions can all add up to global solutions, slowing and eventually halting the upward climb of CO2 concentrations in the atmosphere.