Evidence for Change

Some people take a dim view of the idea that Oregon, as well as the rest of the world, could be expected to continue warming in coming decades. They may cite March snowfall in the Willamette Valley or unpublished comparisons of mean temperatures over a given time period in specific places. Appealing as it is, such evidence hardly constitutes proof that the region is cooling and does not trump rigorous, peer-reviewed science.

It’s important to ask the right questions about data used to reach a conclusion. Are there gaps, either geographically or through time? Were robust statistical methods used to determine if a specific event was indeed unusual? Peer-reviewed research has shown that short periods of cooling can easily be embedded in longer-term warming trends; it’s simply a statistical fact in a time series with a positive trend and a variable system.

Recent cool weather notwithstanding, Oregon has undergone a substantial warming trend over the last 50 to 60 years. What are now considered exceptionally cool seasons were normal 75 to 100 years ago, and seasons now considered normal were exceptionally warm in the same period. If one arbitrarily selects the climatically insignificant period of 5 to 10 years, one can incorrectly conclude that there is no evidence of warming. But further research also shows reasons for the slight decline in global (and Oregon’s) temperatures: A combination of La Niña (when eastern equatorial Pacific sea surface temperatures are 3 degrees to 5 degrees Celsius cooler than normal) and solar minimum (a low point in solar activity) temporarily overcame the gradually increasing effects of greenhouse gases.

Globally, 2011 was the warmest La Niña year ever. Research clearly points to a resumption of the warming as the recent spate of La Niñas wanes and as the solar cycle moves toward maximum. In short, rigorous research tells us so much more than the comparison of averages over arbitrary lengths of time.

The larger point that concerns me is how easily many people dismiss rigorous research in preference for subjective observation. Both are valid ways of adding to the sum of human knowledge, but sometimes the results of research can be counterintuitive and can even contradict what we see with our own eyes.

Take, for example, the patient whose doctor tells him he has a treatable form of cancer. If he feels fine, should he rely only on his subjective feelings? Would he be wise to conclude that his doctor is in “the cancer camp” and wait for clear physical evidence before doing anything?

Or what about the roofer who tells a homeowner that her roof is badly worn and could start leaking in the next storm. Would she be wise to dismiss him as part of the “leaky-roof camp” and ignore him until she actually sees the water trickling through her dining room ceiling?

Why do some of us so flippantly dismiss scientists studying the health of our only planet? Why argue against taking prudent steps now?

Some people may wish that global warming is nonsense. So do I. But I have to accept the evidence provided by thousands of honest, hard-working scientists, meticulously documented during the past 120 years, that says otherwise.

— Phil Mote is the director of the Oregon Climate Change Research Institute