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Sweeping assessment paints a grim picture of Midwest’s changing climate

This year’s National Climate Assessment is the most detailed, plainspoken and dire in a series of reports tracing the impacts of global warming.

Climate change may mean more drought for the Midwest, among other effects.
REUTERS/Jeff Tuttle

Normally I try in this space to focus on environmental subjects or perspectives that are getting scant attention – if they get any at all – from other major media in this part of the world.

Today I want to make an exception for the new U.S. National Climate Assessment, released in draft form late last Friday afternoon.

Despite that difficult timing, Minnesota Public Radio’s Paul Huttner had a fine piece online by early Friday evening, and the Strib’s Bill McAuliffe wrote a good one, too, for Monday’s paper. And coverage of the national-level outlook was extensive.

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But there is much more to highlight from this meta-analysis of research into the miseries that global warming is visiting, and will continue to visit, on our region.

Perhaps you, like me, still encounter optimists or jokesters who continue to bray that a warmer climate regime might actually be a good thing, or at least a mixed blessing, for us here in the northland.

I suggest we print out the assessment’s 38-page Midwest section on heavy paper, roll it into a baton and tote it everywhere we go, the better to whack these dreamers upside the head. And keep whacking till they agree to read the thing.

Meta-analysis of misery

This year’s National Climate Assessment is third in a supposedly quadrennial series, each prepared in a system that should assure credibility to all but the hardest-core deniers (see endnote for details of the process).

It is also, by general consensus, the most detailed, plainspoken and dire of the lot in tracing the impacts of global warming past, present and yet to come.

Here’s the general outlook for the Midwest, excerpted with light compression and emphasis added:

Climate change will tend to amplify existing risks from climate to people, ecosystems, and infrastructure in the Midwest. Direct effects of increased heat stress, flooding, drought, and late spring freezes on natural and managed ecosystems may be altered by changes in pests and disease prevalence, increased competition from non-native or opportunistic native species, ecosystem disturbances, land-use change, landscape fragmentation, atmospheric pollutants, and  economic shocks such as crop failures or reduced yields due to extreme weather events.

These added stresses, when taken collectively, are projected to alter the ecosystem and socioeconomic patterns and processes in ways that most people in the region would consider detrimental.

Much of the region’s fisheries, recreation, tourism, and commerce depend on the Great Lakes and expansive northern forests, which already face pollution and invasive species pressure – pressures exacerbated by climate change. Most of the region’s population lives in urban environments, with aging infrastructure, that are particularly vulnerable to climate-related flooding and life-threatening heat waves.

Extreme-weather ravages are by no means a future prospect only. The report notes that of the 14 U.S. weather-related disasters that made the National Oceanic and Atmospheric Administration’s “billion-dollar list” in 2011, 11 affected the Midwest. (By my count, so did 7 of the 11 on last year’s list.)

Better for crops? Nope

Whatever happened to the notion that longer growing seasons and higher carbon dioxide concentrations at ground level would be good for the crops? Midwest growing seasons have indeed lengthened by nearly two weeks since 1950, but research shows this isn’t necessarily a good thing, because

For corn, small long-term average temperature increases will shorten the duration of reproductive development, leading to yield declines, even when offset by carbon dioxide (CO2) fertilization.

For soybean, yields are likely to increase early in this century due to CO2 fertilization, but these increases are projected to be offset later by higher temperature stress.

Moreover, the report finds that changed weather patterns are likely to deliver a variety of yield-reducing impacts.

High spring temperatures will cause more of the early budding followed by cold snaps that wrecked the cherry crop in Michigan last year. A rising incidence of spring freezing will be bad for many kinds of field crops, corn and beans included. Heat waves will disrupt pollination of these crops and others. And so on.

Although the report acknowledges that computer modeling methods are still not as good for predicting rainfall changes as they are for temperature shifts, it concludes that

Extreme rainfall events and flooding have increased during the last century, and these trends are expected to continue, causing erosion, declining water quality, and negative impacts on transportation, agriculture, human health, and infrastructure.

Flooding carries major human and economic consequences through inundating urban and agricultural land, but also by disrupting navigation in the region’s roads, rivers, and reservoirs. For example, the 2008 flooding in the Midwest caused 24 deaths, $15 billion of losses via reduced agricultural yields, and closure of key transportation routes.

Water infrastructure for flood control, navigation, and other purposes is susceptible to climate change and other forces because the designs are based upon historical patterns of precipitation and streamflow that no longer hold.

An accelerating pace of change

As for recent temperature trends, the assesment looks at not only the extent of change but its pace:

The rate of warming in the Midwest has markedly accelerated over the past few decades. Between 1900 and 2010, the average Midwest air temperature increased by more than 1°F. However, between 1950 and 2010, the average temperature increased twice as quickly, and between 1980 and 2010 it increased three times as quickly. Warming has been more rapid at night and during winter.

And within that trend are the extreme heat events that the assessment says have become more frequent since 1950, and are likely to be a key driver in an overall pattern of increased climate-driven threats to public health. Here’s where the statstics turn especially grim:

During July 2011, 132 million people across the U.S. were under a heat alert – and on July 20 the majority of the Midwest experienced temperatures in excess of 100°F. Heat stress is projected to increase as a result of both increased summer temperatures and humidity. One study projected an increase of between 166 and 2,217 excess deaths per year from heat wave-related mortality in Chicago alone by 2081-2100, depending on the climate model.

Heat response plans and early warning systems save lives, and from 1975-2004 mortality rates per heat event have declined, however, many municipalities lack such plans.

More than 20 million people within the Midwest currently experience air quality that fails to meet national ambient air quality standards. This exposure to degraded air quality due to human-induced emission and increased pollen season duration is projected to be amplified under higher temperatures, and thus increase the human health effects from heat waves.

Increased temperatures could also increase the vulnerability of the Midwestern population to diseases carried by insects and rodents.

Looking to the Great Lakes – which hold more than 80 percent of North America’s fresh surface water – the assessment finds that water temperatures are raising even faster than air temperatures, with results that are complex and mostly unhealthy. Lake Superior’s average temperature, having risen 4.5 degrees since the 1960s, may go up another 7 degrees by mid-century.

Periods of ice cover are shrinking and lake levels have been falling, which might benefit some shipping sectors with long seasons. On the other hand, falling water levels may force the heaviest ships to reduce cargoes or risk going aground in shallower channels and harbors.

In general, the report says, “climate change will exacerbate a range of risks to the Great Lakes region, including changes in the range and distribution of important commercial and recreational fish species, increased invasive species, declining beach health, and harmful blooms of algae.”

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Although I have wanted to focus on the findings for our region, I would be remiss if I didn’t also recommend national coverage of the report, including Juliet Eilprin’s story in the Washington Post. For an overseas perspective, check this piece by the UK Guardian’s science editor, Robin McKie, who wrote:

The report highlights, among other things, that 13 American airports have runways that could be inundated by rising sea levels, and that billions of dollars will be needed to repair Alaskan roads, pipelines, sewer systems, buildings and airports where melting permafrosts are disrupting the landscape. These are problems that will not just affect the US. They will be repeated across the planet.

I invite readers to nominate other good coverage in comments below.

The full assessment, downloadable here as a 147MB file, runs to nearly 1,200 pages. This draft was assembled by a federal advisory panel of 60 scientists and other experts, who engaged nearly 250 others in preparing the report; the draft was reviewed before release by the National Academy of Sciences, and it will be revised after a 90-day public comment period that began Monday. To comment, go here: