What is global warming?

Global warming is the observed increase in the average temperature of the Earth's atmosphere and oce in recent decades. The Earth's average near-surface atmospheric temperature rose 0.6 ± 0.2 °Celsius (1.1 ± 0.4 °Fahrenheit) in the 20th century. The prevailing scientific opinion on climate change is that "most of the warming observed over the last 50 years is attributable to human activities"[1]. The increased amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) are the primary causes of the human-induced ponent of warming. They are released by the burning of fossil fuels

land clearing and agriculture

e and lead to an increase in the greenhouse effect. The first speculation that a greenhouse effect might occur was by the Swedish chemist Svante Arrhenius in 1897

although it did not bee a topic of popular debate until some 90 years later. [2] The measure of the response to increased GHGs

and other anthropogenic and natural climate forcings

is climate sensitivity. It is found by observational [3] and model studies. This sensitivity is usually expressed in terms of the temperature response expected from a doubling of CO2 in the atmosphere. The current literature estimates sensitivity in the range 1.5–4.5 °C (2.7–8.1 °F). Models referenced by the Interernmental Panel on Climate Change (IPCC) project that global temperatures may increase beeen 1.4 and 5.8 °C (2.5 to 10.5 °F) beeen 1990 and 2100. The uncertainty in this range results from both the difficulty of estimating the volume of future greenhouse gas emissions and uncertainty about climate sensitivity. An increase in global temperatures can in turn cause other changes

including a rising sea level and changes in the amount and pattern of precipitation. These changes may increase the frequency and intensity of extreme weather events

such as floods

droughts

heat waves

hurricanes

and tornados. Other consequences include higher or lower agricultural yields

glacial retreat

reduced summer streamflows

species extinctions and increases in the ranges of disease vectors. Warming is expected to affect the number and magnitude of these events; however

it is difficult to connect particular events to global warming. Although most studies focus on the period up to 2100

warming (and sea level rise due to thermal expion) is expected to continue past then

since CO2 has an estimated atmospheric lifetime of 50 to 200 years. [4]. Only a *** all minority of climate scientists discount the role that humanity's actions have played in recent warming. However

the uncertainty is more significant regarding how much climate change should be expected in the future

and there is a hotly contested political and public debate over what

if anything

should be done to reduce or reverse future warming

and how to deal with the predicted consequences.

Global warming is the observed increase in the average temperature of the Earth's atmosphere and oce in recent decades. （以上句子系由維基copy的） stopglobalwarming/sgw_learnmore What is Global Warming? The Earth as an ecosystem is changing

attributable in great part to the effects of globalization and man. More carbon dioxide is now in the atmosphere than has been in the past 650

000 years. This carbon stays in the atmosphere

acts like a warm blanket

and holds in the heat — hence the name ‘global warming.’ 以下是自己打的: Greenhouse gases (e.g. carbon dioxide) trap the sun's energy as heat

therefore when the amount of greenhouse gases increase

the Eath's surface bees warmer and warmer. It is known as the global warming.

Global warming is the Earth getting warmer and warmer.

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