Here is the world temperature diagram from the Hadley Center that some think projects a catastrophic warming (this projection was easier to believe before the cooling of the last several years). The trough-to-peak temperature change from 1910 to 2005 is about .9 degrees C.
This is a diagram from our own National Oceanographic and Atmospheric Administration. The top graph is temperature for the last 900,000 years (as best they can tell). Note that time advances from right to left. The trough-to-peak temperature changes are about 10 degrees C.
The bottom graph is the corresponding estimates of the sea level for the past 140,000 years.
The scary graph from Hadley seems kind of puny in scope when viewed in comparison to the two from NOAA with the much longer time frames and the much larger variations in climate. In the NOAA graphs, the current warming looks a lot like the previous warming episodes when there were no SUVs or coal-fired power plants.
Here’s something else to put in perspective—mass extinction. It seems that most of the species on the earth have survived severe changes in global temperature and sea-level.
A study on speciation looked at hundreds of species of birds and mammals. Here’s the news:
For example, while the closely related Baltimore oriole and black-backed oriole from North America split about 200,000 years ago, the white-edged oriole and spot-breasted oriole from Central and South America split about 4.3 million years ago. The scientists looked at 191 pairs of bird species and 118 pairs of mammal species.
They found that near the equator, sister species evolved into separate groups about 3.4 million years ago on average. By comparison, those in temperate regions split apart roughly 1.7 million years ago.
So, the newer species have been around for hundreds of thousands of years and the average-to-older ones for millions of years. Climate has changed a lot over the last 200,000 years—to say nothing of the past 2 million years.
If species have survived repeated changes in global temperature on the order of 10 degrees; and changes in habitat brought on by sea-level ups and downs of 300 to 400 feet, why will a two-degree change global temperature or a two-foot change in sea level be their undoing?