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.
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
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.
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