Climate change, once considered an issue for a distant future, has moved firmly into the present. Corn producers in Iowa, oyster growers in Washington State, and maple syrup producers in Vermont are all observing climate-related changes that are outside of recent experience. So, too, are coastal planners in Florida, water managers in the arid Southwest, city dwellers from Phoenix to New York, and Native Peoples on tribal lands from Louisiana to Alaska. …
Thus begins the National Climate Assessment issued yesterday morning at the White House, a report so accessible and compellingly written that I saw no point in trying the journalist’s usual task of simplifying science. It continues:
Americans are noticing changes all around them. Summers are longer and hotter, and extended periods of unusual heat last longer than any living American has ever experienced. Winters are generally shorter and warmer. Rain comes in heavier downpours. People are seeing changes in the length and severity of seasonal allergies, the plant varieties that thrive in their gardens, and the kinds of birds they see in any particular month in their neighborhoods.
Other changes are even more dramatic. Residents of some coastal cities see their streets flood more regularly during storms and high tides. Inland cities near large rivers also experience more flooding, especially in the Midwest and Northeast. Insurance rates are rising in some vulnerable locations, and insurance is no longer available in others. Hotter and drier weather and earlier snow melt mean that wildfires in the West start earlier in the spring, last later into the fall, and burn more acreage. In Arctic Alaska, the summer sea ice that once protected the coasts has receded, and autumn storms now cause more erosion, threatening many communities with relocation.
This year’s assessment is the third in a series of reports ordered by Congress in 1990 on what was to be a quadrennial schedule. It hasn’t worked out that way: The Clinton administration took its time on the first assessment, bringing it out in 2000. The Bush administration just took a pass, leaving to President Barack Obama’s team to produce the second, in 2009, and now the third.
All three have been characterized by solid science, transparent documentation and clear-eyed, expert analysis by large panels (about 60 principal authors were convened for this edition, and they were aided by more than 250 other collaborators).
But this year’s report makes big advances in reader utility and appeal, especially in its visual style and an interactive approach that lets you chart your own path through its mass based on what particular impacts, parts of the country or other special interests hold your greatest concern.
You can tell it’s a report meant to be read by the wider public, rather than merely referenced by their media gatekeepers. We can only hope this strategy pays off, because the time available for meaningful action to mitigate climate disruption — the report does not shrink from that apt and accurate terminology — is shrinking fast.
Emphasis on here and now
Of necessity the report discusses the current state of climate science and modeling, but its primary focus is, first, on the observable impacts plainly traceable to changing climate, and then on possible coping strategies.
Climate scientists have long spoken with confidence about the general problem of global warming, and also about possible solutions. Over the last several years they’ve been shedding a longstanding reluctance to talk about the middle piece — the linkages between here-and-now changes and complex global systems — and the report says this shift, too, represents advances in understanding.
What is new over the last decade is that we know with increasing certainty that climate change is happening now.
It is notable that as these data records have grown longer and climate models have become more comprehensive, earlier predictions have largely been confirmed. The only real surprises have been that some changes, such as sea level rise and Arctic sea ice decline, have outpaced earlier projections.
Two prime examples:
Prolonged periods of high temperatures and the persistence of high nighttime temperatures have increased in many locations (especially in urban areas) over the past half century. High nighttime temperatures have widespread impacts because people, livestock, and wildlife get no respite from the heat. … Evidence indicates that the human influence on climate has already roughly doubled the probability of extreme heat events such as the record-breaking summer heat experienced in 2011 in Texas and Oklahoma.
Water quality and quantity are being affected by climate change. Changes in precipitation and runoff, combined with changes in consumption and withdrawal, have reduced surface and groundwater supplies in many areas. These trends are expected to continue, increasing the likelihood of water shortages for many uses. Water quality is also diminishing in many areas, particularly due to sediment and contaminant concentrations after heavy downpours.
Closeup on the Midwest
As for potentially positive effects of a warming climate, the report highlights just two as it looks to the near future — longer growing seasons for some crops in some places, and longer availability of shipping conditions on the Great Lakes — and these would seem to favor Minnesotans.
However, the overall impacts laid out in the report actually seem to especially disfavor the eight-state Midwest region lying east of the Great Plains and north of the Ohio River:
Extreme heat, heavy downpours, and flooding will affect infrastructure, health, agriculture, forestry, transportation, air and water quality, and more. Climate change will also exacerbate a range of risks to the Great Lakes …
Direct effects of increased heat stress, flooding, drought, and late spring freezes on natural and managed ecosystems may be multiplied 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.
Other points that caught my eye in the Midwest section:
- The region has been warming somewhat more rapidly than the nation overall, when temperatures of the past 22 years are compared with an average for the first 60 years of the last century; the northern portions of Minnesota, Wisconsin and Michigan have been warming at some of the highest rates in the country — more than 1.5 degrees F.
- Looking to the so-called “billion-dollar list” produced annual for the insurance industry, “in 2011, 11 of the 14 U.S. weather-related disasters with damage of more than $1 billion affected the Midwest.”
- Though the growing season for crops like corn and soybeans has lengthened by about two weeks since 1950, as the last-freeze dates have come earlier, this is not purely good news. “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) stimulation., For soybeans, yields have a two in three chance of increasing early in this century due to CO2 fertilization, but these increases are projected to be offset later in the century by higher temperature stress.”
- We can expect to lose “many iconic tree species such as paper birch, quaking aspen, balsam fir, and black spruce . . . across the northern Midwest as they shift northward.” While mountain species can reach cooler climes by climbing, higher, and traveling just a few miles, “in flat terrain like the Midwest [trees] must move as much as 90 miles north to reach a similarly cooler habitat.”
- The Midwest does have an opportunity to contribute disproportionately to solutions based on carbon-emission reductions in the energy sector, that’s a reflection of the painful fact that with existing systems, “energy use per dollar of gross domestic product is approximately 20% above the national average, and per capita greenhouse gas emissions are 22% higher than the national average due, in part, to the reliance on fossil fuels, particularly coal for electricity generation.”
Finally, while there may be benefits in further lengthening of the Great Lakes shipping season, which expanded an average of eight days per year between 1994 and 2011, negative effects of changing climate include higher surface-water temperatures in summer, less ice cover in winter and a corresponding increase in the growth of blue-green and toxic algae.
And long-term declines in overall lake levels could translate into shallower shipping channels and thus less cargo per vessel, potentially offsetting any lengthening of the operating season.
