The Facts

• 71% of the Earth is covered by its ocean.
• 60% of the heat from the equator is moved North and South by ocean currents.
• The North Atlantic circulation system... carries warm surface water northwards and returns cold deep water to the south. It results in a transfer of free heat to the atmosphere equivalent to 30,000 times the power-generating capacity of the UK
  Source: Natural Environment Research Council

What is happening?

One of the primary sources of information about climate change are the Assessment Reports from the Inter-governmental Panel on Climate Change (IPCC). These reports are written by a team of scientists and contain clear facts about what is happening. Here's a selection:

Temperatures are increasing

• The global average surface temperature has increased over the 20th century by about 0.6 degrees Celsius.
• Globally, it is very likely that the 1990s was the warmest decade and 1998 the warmest year on record. Records have been kept since 1861.

Snow cover and ice extent have decreased

• Satellite data shows a decrease of about 10 percent in the extent of snow cover since the late 1960s.
• Ground-based observations show that there is very likely to have been a reduction of about two weeks in the annual duration of lake and river ice cover in the mid and high latitudes of the Northern Hemisphere, over the 20th century.
• There has been a widespread retreat of mountain glaciers in non-polar regions during the 20th century.
• Northern Hemisphere spring and summer sea-ice extent has decreased by about 10 to 15 since the 1950s. It is likely that there has been about a 40 percent decline in Arctic sea-ice thickness during late summer to early autumn in recent decades and a considerably slower decline in winter sea-ice thickness.

Temperatures will continue to increase during the 21st century

• Scientists have developed sophisticated systems that allow them to predict what will happen to our climate in the next 100 years. These systems aren't perfect and there is a range of possible outcomes. However, all the different systems agree that temperatures will rise. The likely increase is somewhere between 1.4 and 6.0 degrees Celsius, and probably towards the upper end of that scale.
  

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