The most basic prediction of climate change science is global warming. But is it really happening?
It isn’t easy to calculate average global temperature. Which measurements should be included, and how much should each be weighted? Do we want air temperature, or water temperature?
Different calculations therefore do not always agree totally. But the picture is quite clear.
Global temperatures are rising …. fast
This graph from NASA shows how much global average temperature has risen since accurate measurements are available. The temperatures are expressed as the difference from the average temperature in the 1951-1980 period. Thus we can see that average global temperature has risen about 0.5 degrees Celsius in the past few decades.
The last decade has been the hottest on record
Some people have claimed that temperatures are no longer rising, and the hottest year on record was a decade ago. That claim was misleading, because we can expect weather to vary about the average trend, but it is the trend that is important.
But the claim is no longer even technically true. These are the facts on worldwide average temperatures (from Wikipedia):
- The hottest year on record occurred in 2005, with 2010 second and 1998 third.
- 9 of the hottest 10 years on record occurred since 2000.
- All of the 20 hottest years on record occurred since 1987.
- The rate of change in world temperature is faster than any previous change.
Climate scientists have used tree rings and ice cores to estimate global temperatures for the past 2000 years (Wikipedia), and have found that the temperature has virtually never been above the 1951-1980 average over that time. What we are experiencing is hotter temperatures than have been known for at least two millennia, and probably far longer.
It cannot be doubted
The world is warming, at an unprecedented rate, and is hotter than it has been for a long time. This cannot be doubted by anyone who looks at the evidence.