I have a geologist friend that presented me with the argument that the problem with the man causes climate change hypothesis is that it only looks at a small period , and that most of the change today can be explained by something called milankovitch cycles and presented me this article http://www.paulmacrae.com/?p=62
Is there any response to this sort of argument ?? If so where can I find articles that talk about this matter ? Most of the people against the idea of global warming have been cranks, but this friend is a serious geologist not just random guy on the internet. Thanks in advance =)
I haven't read the full article yet (I might read it some time over the next few days and give a more detailed response if you want), but the first book I ever read on climate change was written by a Dutch geologist who made a similar argument. In case you're curious, here
's a good primer on what Milankovitch cycles are. Skepticalscience.com is usually reliable and based on the peer reviewed literature. They also have a list of most used climate myths
. For example, here's
an article that addresses the frequently heard point that we're heading into a new ice age
because of Milankovic cycles (so note that this argument tells us to expect cooling, not warming, from those same cycles). Not exactly what you need, but pretty close. Here's
another post that addresses the idea that the current warming is natural. Many more related tropes in the list of arguments.
Generally speaking, we know that humans are causing the warming for a variety of reasons. The first is basic theory; we know from laboratory experiments that CO2
is a greenhouse gas. We know for a fact that we are pumping large quantities of it into the atmosphere, therefore something pretty amazing would have to occur for us not to influence the climate. Svante Arrhenius predicted global warming as early as 1896 based on his studies of CO2
. Related is palaeodata, which shows that increased concentrations of CO2
in the distant past are associated with warmer temperatures (although I should note here that CO2
was a feedback mechanism as opposed to the primary driver behind such changes, which is why deniers sometimes bring up the "CO2 lags temperature"
canard - but the point is that the temperature variations can't be explained without including the CO2
feedback). Third, we can take (and have been taking) spectroscopic satellite readings of longwave radiation at the top of the atmosphere, and we can see that, over time, there is increased absorption in the parts of the spectrum associated with CO2
. In other words, CO2
is "trapping" energy that otherwise would have radiated back out to space. And finally, we have sophisticated models of the climate system that represent the best knowledge we have on the subject. When we use models that only include natural drivers of change (which include Milankovic cycles), we cannot model the temperature changes since the industrial revolution, but we can model temperature variations of earlier periods pretty well. Only when we include human drivers of climate change, can we faithfully reproduce historical temperature trends.