What evidence do we have of climate change?

Answer 1

Observable evidence includes:

• reduction of the permanent ice cover at the north and south poles
• reducing size of glaciers
• northern movement of new animals/insect species
• loss of permafrost
• breeding habit changes in seals and walruses

Other related but not as confirmatory evidence includes:

• number of severe weather events
• apparent location of sunrise and set in the north and south due to changed air density
• northern aboriginal observations of hunting and weather

A:

There are several evidences that point to the changing climate. One of the major ones is the fact that Arctic and Antarctic ice is melting at an accelerated level.

Answer 2

First of all, there is no such thing as 100% evidence in science. Scientists work with levels of probability and likelihood. The higher the level of probability and likelihood, the higher the scientific 'evidence'.

The most comprehensive scientific research into Climate Change is that of the IPCC which since the end of 1988 has been studying climate change, its causes and effects as well as developing recommendations to mitigate it. Periodically, the IPCC publishes reports on their latest findings (called Assessment Reports or ARs). The IPCC does not conduct scientific research itself; it studies all the available scientific papers related directly or indirectly to climate change. For the latest assessment 6,000 such scientific papers were used.

The most recent IPCC report from 2007 (with a new one due in 2014) labels the warming of the climate as "unequivocal as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level".

NASA, at their Global Climate Change website lists the following as evidence of Climate Change:

• rising sea levels (due to land-based ice melting and the expanding of warming sea water) at a faster rate then before;
• global temperature rise with the 20 warmest years on record since 1981 while other temperature factors such as the sun were at its lowest intensity;
• warming oceans;
• decreasing ice sheet extension on Greenland and Antarctica;
• decreasing Arctic ice sheet extension;
• glaciers retreating globally;
• an increase in ocean acidification;
• global increase in extreme weather events (as predicted in the 3rd and previous IPCC assessment reports).

Answer 3

fossils, and the rock cycle ;)