What Caused the Ice Ages and Other Important Climate Changes Before the Industrial Era?

Global climate is determined by the radiation balance of the Earth. This is influenced by three different factors: a change in the incoming solar radiation, an alteration in the amount of solar radiation reflected, and a change in the amount of infrared radiation emitted from the Earth’s surface (eg. Changes in greenhouse gas concentrations). There is strong evidence that ice ages occurring over the last 3 million years are related to regular variations in the Earth’s orbit around the Sun, known as Milankovitch Cycles.


Is Sea Level Rising?

It is estimated that sea levels have been stable from between 2000 and 1000BC up until the late 19th century. During the 20th century, sea levels have risen globally at an average of 1.7mm per year. Since 1993, global sea level has risen by an average of 3mm per year. However, sea levels are not rising uniformly around the world. In some regions rates are several times the global average, while in other regions sea level is falling.


Is the Amount of Snow and Ice on the Earth Decreasing?

Yes. Observations show a global-scale decline of snow and ice, particularly since 1980 and increasingly since the late 1990s. Most mountain glaciers are retreating. Snow cover is disappearing earlier in the spring in many regions. Arctic sea ice is retreating in all seasons, most dramatically in the summer. Reductions in permafrost and river and lake ice are evident, as well as thinning of polar ice off the coasts on Greenland and Antarctica.


Has there been a Change in Extreme Events?

...like Heat Waves, Droughts, Floods and Cyclones?

Heat wave frequency has increased since 1950. The extent of regions affected by droughts has also increased since this time, specifically in southern Asia, northern Africa, and northern North America. However, an opposite trend is observed in eastern North and South America, and no significant trend is apparent for Europe.


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