Discerning climate change from normal variability

Hot? Yes, and dry, too. But can you blame it on global warming?

This article was written in June 2012 during Colorado’s blistering heat wave after a winter parched of snow and a rash of fires. It was distributed by Writers on the Range.

by Allen Best

Knee-high by the Fourth of July is the saw in Colorado’s corn-growing country. This year, hurried by the hot weather of spring, the stalks stood waist-high against my 6-foot-2 frame in a field that I visited between Mead and Loveland on June 23, the first day of summer.

We have had many outliers of this fecundity: early peaches, corn and cantaloupe, plus cicadas in June instead of August. This year we also had six months of above-average heat, if nothing approaching the all-time record of 114 degrees set in the 1930s and 1950s, two other times of heat and drought. We also had those huge, horrible forest fires.

Is global warming to blame? And more specifically, is it human-caused warming?

The conventional answer of climate scientists is that is that climate change can only be discerned clearly in the rear-view mirror. The scientific record is clear: the planet is warming. and the changes are consistent with models assembled to predict the effects of greenhouse gases accumulating in the atmosphere. Daily record high temperatures occurred twice as often as record lows from 1999 to 2009 across the continental United States, according to an analysis led by Dr. Gerald Meehl, of the National Center for Atmospheric Research in Boulder.

But weather extremes – droughts and deluges, heat waves and hurricanes – are trickier. The abnormal events are harder to pick out from what climate scientists call the noise of historic variability.

Some scientists, most prominently Dr. Kevin Trenberth, of the National Center for Atmospheric Research, argue that extreme weather events have moved beyond the range of historic variability. For him, we have enough rear-view perspective to draw conclusions. He wants other climate scientists to stride more briskly to the lectern to admit that we already live in a new, human-altered normal, what some call the anthropocene.

In Colorado Springs, 60 mph winds blew fire down this hillside and into a subdivision.Photo/Allen Best

In Colorado Springs, 60 mph winds blew fire down this hillside and into a subdivision.
Photo/Allen Best

Do journalists also have a responsibility to connect the dots of today’s weather with broad climatic shifts? And should we further link today’s weather with the accumulating greenhouse gas emissions that nearly all scientists agree are heating the globe?

A watchdog group called Media Matters this summer found that CNN, the Wall Street Journal and other national news media change rarely mentioned climate change in their coverage of wildfires. The group asked nine wildfire experts whether they should have. Most said yes.

“Absolutely, journalists who care to look at the bigger picture should be stating that we already are seeing an acceleration of western wildfire activity in the last 30 (years), and some of that acceleration is tied to the trend of earlier snowmelt and hotter, drier summers,” responded Dr. Steven W. Running, director of the Numerical Terradynamic Simulation Group at the University of Montana. “If the media do not connect these dots, the public probably assumes these latest events are only natural variability and ‘bad luck,’ when in reality they are a glimpse into a more common future if carbon emissions continue to rise.”

Two on the panel dissented. “Even the big fires currently blazing away are within the range of historic climates,” said Dr. Steven J. Pyne, of Arizona State University. “My personal evaluation of the situation is that we do not currently know enough to make reliable predictions about how global warming will impact future fires,” said Dr. Jon E. Keeley of the U.S. Geological Survey’s Western Ecological Research Center.

None of the experts denied the existence of climate change, nor of human complicity. Rather, the minority disagree about the relative certainty of human causes in this heat wave, that drought, or those wildfires.

The broad brushes are clear enough: Computer climate models have predicted much of what is occurring: warming temperatures, ebbing sea ice in the Arctic, rising sea levels.

In the West, we have a very thin record of what constitutes normal, both in terms of temperatures and precipitation. Some 900 years ago, megadroughts that lasted decades may have caused the Ancestral Pueblo to abandon their cliff dwellings at Mesa Verde. What were bark beetle infestations like during those droughts? Wildfires? We don’t know. Our understanding of “normal” is limited.

The Yampa River in Steamboat Springs was reduced to a trickle last year. Photo John F. Russell/SteamboatToday.

The Yampa River in Steamboat Springs was reduced to a trickle last year. Photo John F. Russell/SteamboatToday.

That’s the problem with this story of global warming. We crave simple lines of cause and effect, black and white, winners and losers. This story has nuance. It’s difficult to distill these uncertainties of giant risk in the distant future in a story about today’s weather or this summer’s corn crop.

But even if we can’t pin the tail of global warming on every weather extreme, we must continue talking about the looming risk. It’s too bad there’s barely been a whisper at the national political conventions.

 

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About Allen Best

Allen Best is a Colorado-based journalist. He publishes a subscription-based e-zine called Mountain Town News, portions of which are published on the website of the same name, and also writes for a variety of newspapers and magazines.
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5 Responses to Discerning climate change from normal variability

  1. R James says:

    Actually, the changes aren’t consistent with the models. The IPCC has had to gradually reduce it’s expectations of temperature increase, and AR5 will have to reduce further. According to the Hadley Centre data, real temperature now lies below even the most conservative model predictions.

    Now that it’s been at least 16 years since we’ve experienced any warming, it’s hard to keep the momentum going.

    • jjhman says:

      “Now that it’s been at least 16 years since we’ve experienced any warming”

      This is one of the repeating canards of the professional climate skeptics. However the year 2010 is now the hottest on record, tying 2005. Yet it is true that we are in a trend of slower warming. This is consistent with the pattern of past warming analysis which includes cyclic changes caused by changes in the sun’s output, el nino/la nina weather patterns and exchanges of heat energy between the oceans and the atmosphere.

      Unless Mr. James is a member of the IPCC Working Group I he has not better guess of what the IPCC is going to report than he has of whether its going to rain next Labor Day.

      • R James says:

        Leaked details or the draft report indicate that the bottom range of predictions will be revised down. It’s probably about 9 months before the report will be released, but if there is still no warming trend by then, their current predictions will look even more erroneous.

        Some data sets showed 2010 to be hotter after they included old Arctic data, which was previously excluded (eg Hadcrut – May 2012). I wonder if this data would have suddenly been included if it pushed the trend downwards? The scientific process is to test an hypothesis against real data. If they don’t match, then change the hypothesis. In climate science, they simply change the data. This is not good science.

    • Jan Freed says:

      Some folks like to play scientist, but when ill wouldn’t think of playing doctor.

      Cooling? Losing momentum? Natural fluctuations? The last 15 years show the 12 hottest years on record. This 2000-2010 decade has been the very hottest on record. We have had over 350 consecutive (!) months of higher than average monthly temperatures. In a stable climate one would have roughly equal numbers of cooler and warmer months. This is like flipping heads 350 times in a row, beating chance odds of one divided by the number of stars in the universe.

      Chery picking will lead to false conclusions. The usual fossil fools, the usual suspects, the usual distortions. Ho hum.

  2. Jan Freed says:

    I recently attended a joint conference of California fire marshals and insurance companies. One marshal stated our fire season is 78 days longer than the former average. With today’s earlier snow melt conditions are drier. Drier things burn more easily, right?

    Another marshal spoke of an area of forest that was burning where typically it would have been under a few feet of snow. Forests that have never been “managed” are increasing in acres burned.

    Also, trees that are stressed by heat, drought and insects do not survive fires as well as healthy trees, so there are fewer trees (and seeds) to restore burned forests after the fires have gone.

    ‘California this summer has 5% of its former average water supplies.’ I have to fact check that, as that is just too incredible and depressing, but a professor of water management claims it is so.

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