I recently started getting daily environmental digests from ScienceDaily. Each newsletter has more items in it than I have time to read, but those I've checked out have been interesting, informative, and well sourced. Two items in this morning's update combined to reshape my understanding of anthropogenic climate change.
One of the emotional hurdles a lot of people have to get over in order to accept the idea of human-caused climate disruption is the sense that the world is so big and humans are so small. How could we possibly be affecting something as large and complex as global climate? Sunspots ... sure! The sun is bigger than the Earth, so the sun can affect our climate. Long-cycle periodic variation that's beyond anyone's understanding -- a kind of natural rhythm of the planet ... OK, that seems big enough even if cause and effect are entirely unknown. But, to many folks, saying that humans can change the climate seems somewhat hubristic.
I may be totally off-base here, but I also think that the specific span of time across which human activity is explained as causing climate disruption presents an emotional hurdle. Most explanations ascribe anthropogenic greenhouse gas impacts to the increase in fossil fuel combustion that started with the Industrial Revolution and has accelerated significantly since. This is the period in which virtually everything we think of as advanced or modern came into being -- the lifespan of marked Western military and cultural supremacy. Hearing that the things that put the USA and other OECD nations at the top of the heap are the things that are causing climate problems causes many Americans to feel that civilization-as-we-know-it is being attacked.
This is where the two items (here and here) have started reshaping my thinking. Both articles indicate that human impacts on climate go back much farther than the mid-19th century. Presenting at the recent meeting of the American Geophysical Union, two Stanford geological and environmental researchers have proposed that large-scale reforestation in the Western Hemisphere -- a result of decreased agriculture due to depopulation as a result of pandemics from exposure to European diseases -- actually lowered CO2 levels enough to contribute to the so-called Little Ice Age (1500 - 1750). (A good description of Native American civilization before the pandemics is given in Roger Kennedy's Hidden Cities which, I fear, is out of print.) Going back even further, a report from a team of climatologists at UW-Madison is showing mild but significant human-induced climate change dating from the Agricultural Revolution (around 4000 - 6000 BCE).
Are both of these presentations 100% on the money? Probably not -- both research projects continue, and our understanding will probably evolve or even shift significantly. But the very prospect that humans have been contributors to climate for millenia might somehow blunt the "attack on modern civilization" perception, shouldn't it? And the UW research even raises the prospect that human activity helped ward off a cyclic full-blown (not "Little") ice age; unintentionally or not, we can change climate for the better, as well as for the worse.
True, none of this information changes the hard facts of 21st Century ecological challenges. But, at least to my mind, they reframe the situation in a somewhat more manageable light.