These studies build on earlier work that has shown seasonal shifts and changes in species distributions, along with ecological alteration, in response to the moderate warming of the 20th Century.
And what precisely does man have to do with this? Or better, what can or should man do about it seeing as temperatures seem to be returning to where they were 2000 years ago and therefore "ecological alteration" and "species distributions" are simply returning to their nominal state in response to conditions prevalent before "20th Century warming".
Figure 1-2 Climate of the last 2400 years
Figure 1-3 Climate of the last 12,000 years
And what precisely does man have to do with this? Or better, what can or should man do about it seeing as temperatures seem to be returning to where they were 2000 years ago and therefore "ecological alteration" and "species distributions" are simply returning to their nominal state in response to conditions prevalent before "20th Century warming".First, mankind's activities may have something to do with the current rate of warming. We'll be more sure of that (or not) in a few years. Second, the warming rate over the 20th century, 0.6 C, is faster by about 2x than any century in the past 2000 years. The "squeezed" nature of your graph doesn't show this very well. Natural ecosystems can adapt to a temperature rate of change maximum of about 2 C/century, which may be (note the qualification) the rate of temperature rise that has taken place since the mid-1970s. So, if mankind's activities are responsible for the current rate of temperature change, then the possible of ecosystem collapse, rather than adaptation, exists. I think the best estimates of the rate of temperature change in the 21st century are about 2-3 C, and a very recent paper first-authored by Patrick Michaels appears to support my opinion. So the 21st century could be a period where many ecosystems will be significantly stressed by rapid climate change.