In the last years, Earth's average surface temperature increased by about 0. As a result, anthropogenic global warming has recently become a major concern for humanity. Such concerns are supported worldwide by the wide majority of climatologists. Global warming is an increase in temperature in addition to the natural greenhouse effect.
But global warming can alternatively refer to simply the observation of warming, without iplying the cause s of that warming. As seen in the above chart, there have been two main episodes of warming in the last years or so Warming stopped around The most popular explanation for global warming is the burning of fossil fuels, mainly petroleum and coal, which produces carbon dioxide as one of the by-products.
The potential warming effect of the extra CO2 is through its ability to absorb and emit infrared radiationwhich is the type of radiation the Earth continually loses to outer space in response to heating by sunlight.
This makes carbon dioxide a greenhouse gasalbeit a weaker one in the atmosphere than water vapor. The net effect of greehouse gases on is to keep the lower layers of the atmosphere warmer that they otherwise would be without those gases. Therefore, it has seemed reasonable to assume that an increase in greenhouse gases would lead to warming.
But the big question is, how much warming? How serious will global warming be? We don't know for sure, and there is much debate in the climate research community over this very question.
The consensus of opinion is that a warming of about 0.
F every 10 years is expected for the next years or so. The reason why there is so much uncertainty, though, is not because of the direct warming effects of more carbon dioixde, which are relatively weak. The main uncertainty is whether clouds and other components of the climate system will change in a way that amplifies -- or reduces -- the relatively weak warming effect of the extra carbon dioxide.
These indirect effects are called feedbacks, and they will determine the extent to which manmade global warming is a problem or not. The processes by which clouds and water vapor -- the 2 main feedbacks -- are maintained in the atmosphere are very complex.
For instance, clouds on a whole act to cool the Earth in response to heating by the sun. But the consensus of scientific opinion is that this will reverse with the slight warming from increasing carbon dioxide.
Again, how clouds will change with global warming will be critical, as they could either amplify the warming, or reduce it. While water vapor feedback is more widely accepted to be an amplifying influence on warming, this is not obvious since warming-induced change in precipitation formation processes in rain systems is not well understood, and could cancel out the greater surface evaporation rates that would accompany surface warming.
If those rain systems become more efficient at converting water vapor into precipitationthis would act to offset global warming.
Cloud and precipitation-related feedbacks are so uncertain that it is difficult to assign any level of confidence to global warming projections.
But what about the warming to date? While there is some uncertainty over how much warming has occurred over the last 50 to years, it is pretty certain that warming has, indeed, occurred. But is that warming unusual?Curiously, the temperature graph preferred by the Intergovernmental Panel on Climate Change, the famous “hockey stick,” smooths out the Medieval Warm Period and Little Ice Age to create an impression that twentieth-century warming is “the warmest in 1, years” (Figure 2).
What is global warming?
In its most commonly used sense, “global warming” refers to the gradual warming of global-average temperatures due to the slowly increasing concentrations of man-made atmospheric greenhouse gases, primarily carbon schwenkreis.com global warming can alternatively refer to simply the observation of warming, without iplying the cause(s) of that warming.
As the volume of greenhouse gases increases yearly, scientists are warning that the global average temperature could increase by as much as 6 degrees Celsius over the next century, which would cause our world to change radically. global warming scenariosGraph of the predicted increase in Earth's average surface temperature according to a series of climate change scenarios that assume different levels of economic development, population growth, and fossil fuel use.
The assumptions made .
Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. The term commonly refers to the mainly human-caused observed warming since pre-industrial times and its projected continuation, though there were also much earlier periods of global warming.
Dr. Tapio Schneider discusses the science behind human-induced climate change. He is a climate scientist and Professor of Environmental Science and Engineering at the California Institute of .