There is clear evidence to show that climate change is happening. Measurements show that the average temperature at the Earth’s surface has risen by about 1°C since the pre-industrial period. 17 of the 18 warmest years on record have occurred in the 21st century and each of the last 3 decades have been hotter than the previous one. This change in temperature hasn’t been the same everywhere; the increase has been greater over land than over the oceans and has been particularly fast in the Arctic.
Range in perspectives
Everyone has been affected by climate change but also everything like the Arctic sea and glaciers in it. As the Arctic warms, sea ice is decreasing rapidly. In the Antarctic, sea ice has slowly increased, driven by local changes in wind patterns and freshening sea water. However, in recent years Antarctic sea ice has stopped growing. Over the past few decades the ice sheets (the great masses of land ice at the poles) in Greenland and the Antarctic have shrunk, as have most glaciers around the world.As land ice melts and the warming oceans expand, sea levels have risen. Global sea level has risen by around 20 cm over the past century, likely faster than at any point in the last 2,000 years. The rate of sea level rise has increased substantially over the 20th Century and further rise this century is inevitable – how much depends on the amount of human greenhouse gas emissions.
Rising levels of carbon dioxide and other greenhouse gases, such as methane, in the atmosphere create a ‘greenhouse effect’, trapping the Sun’s energy and causing the Earth, and in particular the oceans, to warm. Heating of the oceans accounts for over nine-tenths of the trapped energy. Scientists have known about this greenhouse effect since the 19th Century.The higher the amounts of greenhouse gases in the atmosphere, the warmer the Earth becomes. Recent climate change is happening largely as a result of this warming, with smaller contributions from natural influences like variations in the Sun’s output.Carbon dioxide levels have increased by about 45% since before the industrial revolution. Other greenhouse gases have increased by similarly large amounts. All the evidence shows that this increase in greenhouse gases is almost entirely due to human activity.