Climate change

As an on-air weather person I am sometimes asked what I think about global warming. My impression is that most people are pretty skeptical about the subject. Since few of the people that I talk with have degrees in atmospheric physics or paleoclimatology, I assume that their skepticism derives more from doubts as to whether humans could really affect something as apparently unchanging as climate.

And yet we know that our planet's climate has been drastically different. Fossil records show that over the eons there have been palm trees in Alaska and glaciers in the south. Until recently, though, it was assumed that the earth's climate generally tended to change only gradually and slowly. Only the most obstinate life forms would have been unable to adaptÉ.

But new research is suggesting something new and troubling: that the climate system has in the past changed more dramatically and abruptly than anything we are used to. Far from tracing out a long smooth curve over time, growing evidence suggests that the earth's climate may jump back and forth between very different stable states. In fact some records suggest that the climate may in the past have warmed by more than 10 or 20 degrees in just a decade or two. Needless to say, such an abrupt change now would be catastrophic.

Not everything is understood about what triggers these shifts, but records show that they are associated with changes in atmospheric chemistry, ocean currents and vegetation. Could humans really induce such a change? Currently scientists do not know enough to definitively answer that question. But the troubling implication of this new research is that in the past, small changes in the system may have caused large shifts in climate.

Are humans causing global warming now? That is more difficult to answer, but most scientists feel that at least part of our current warming is indeed due to greenhouse gases and deforestation. But even those that are still skeptical are concerned about the future. There is no doubt that we are conducting a giant physics experiment with the only climate we have. There is a significant risk that the results may come in more quickly than earlier imagined.

Brian Alworth is a meteorologist at KFVS-TV channel 12 in Cape Girardeau.