EarthTalk: How are droughts and wildfires caused
by global warming? I thought warming mostly brought on wet
and flooded conditions.
—David Mossman, Albuquerque, NM
throwing the planet’s climate out of whack,
global warming is likely to cause more extreme weather
events -- and not just rain, snow and flooding but
more droughts and wildfires, too, sometimes within
the same regions that at other times experience
extreme wet weather.
throwing the planet’s climate regulation systems out
of whack, global warming is likely to cause more extreme
weather events of every kind, including additional precipitation
and flooding in some cases and more drying and drought in
others—sometimes within the same region.
to the Union of Concerned Scientists (UCS), a leading non-profit,
increased temperatures on the Earth’s surface due
to global warming accelerates evapotranspiration, an otherwise
natural process that takes moisture from land, plants and
water bodies and moves it skyward into the atmosphere.
drier regions, evapotranspiration may produce periods of
drought—defined as below-normal levels of rivers,
lakes and groundwater, and lack of enough soil moisture
in agricultural areas,” reports UCS. “Precipitation
has declined in the tropics and subtropics since 1970. Southern
Africa, the Sahel region of Africa, southern Asia, the Mediterranean,
and the U.S. Southwest, for example, are getting drier.”
Even areas that are typically wet, says the group, can experience
long, dry spells between extreme rainy periods.
drying trend is expected to continue through mid-century
as the amount of land affected by drought grows significantly.
Water resources in affected areas are predicted to decline
by as much as 30 percent. “These changes occur partly
because of an expanding atmospheric circulation pattern
known as the Hadley Cell—in which warm air in the
tropics rises, loses moisture to tropical thunderstorms,
and descends in the subtropics as dry air,” adds UCS.
“As jet streams continue to shift to higher latitudes,
and storm patterns shift along with them, semi-arid and
desert areas are expected to expand.”
National Wildlife Federation (NWF) adds that the sea level
rise expected to accompany global warming (as the polar
ice caps melt) could further complicate matters for water-constrained
areas by contaminating critical inland underground freshwater
reserves with salt (so-called “saltwater intrusion”).
effect of unmitigated global warming will be a increased
frequency of large wildfires and an expansion of burned
over areas in already fire-prone regions like much of the
Western U.S. NWF reports that researchers there are already
noticing longer fire seasons, drier conditions persisting
later into the year, and an increased frequency of lightning
as thunderstorms are becoming more frequent and severe.
The group adds that forest fires are expected to burn over
twice as much of today’s affected areas across 11
western states by later this century if conservative predictions
about warming come true.
what can be done? NWF stresses that every one of us can
play a role by cutting back on our fossil fuel use (less
driving and flying, less home heating and cooling, more
efficient appliances, etc.). Another way to help is to take
into account our own water use and making a concerted effort
to cut back and conserve this most vital of all natural
resources. NWF also wants land managers and policymakers
to consider global warming when choosing water management
strategies to meet multiple demands and to work to protect
natural forest and wetland systems that absorb flood waters
and provide efficient water storage.
NEW SET OF ANSWERS IS FEATURED EACH WEEK!
EarthTalk: What is “biomass” and
why is it controversial as a potential source of energy?
—Edward White, New Bedford, MA
can be a part of the effort to cut back on fossil
fuels, but only if it is harvested and used in ways
that reduce pollution, cut emissions and protect
forests. Pictured: A biomass-burning power plant.
Biomass is plant
matter that is burned as a source of energy. Fallen or cut
wood that is burned for heat is one primary form of biomass,
but another includes plant or animal matter that is converted
the International Energy Agency (IEA), which was formed
during the oil shocks of the early 1970s to help ward off
future energy shortages, biomass combustion is a carbon-neutral
process because the carbon dioxide released at burning has
previously been absorbed by the plants from the atmosphere.
reports IEA, include agricultural residues, animal manure,
wood wastes, food and paper industry residues, municipal
green wastes, sewage sludge, and a large variety of grasses
But while biomass
may be in theory carbon-neutral, green groups point out
that there is no free lunch. The Natural Resources Defense
Council (NRDC), for example, points out that some American
timber companies are targeting whole trees from forests
as an easy source of biomass and are pressuring Congress
to open up additional National Forest acreage for this form
of energy generation.
NRDC says that,
practically speaking, burning whole trees for biomass energy
is far from carbon-neutral, given that the carbon dioxide
that trees accumulate over decades is suddenly released
into the atmosphere upon combustion, just like when coal
is burned. “But unlike coal, however, trees will continue
to absorb carbon if left alone.” Therefore, the burning
of forests for biomass energy both emits considerable amounts
of carbon and destroys an important way carbon is prevented
from entering our atmosphere.
isn’t the only problem with biomass. Burning biomass
also produces sulfur dioxide, nitrogen oxides, particulate
matter and other toxins harmful to our health. Two California
wood-fired power plants were fined $830,000 under the Clean
Air Act recently for violating emissions standards.
And then there
is the issue of the efficiency of biomass as a fuel feedstock.
Researchers have found that some common forms of biomass
yield only 25 or 30 percent the amount of energy as an equivalent
amount of coal. The 2011 closure of a biomass conversion
plant in Georgia that reportedly spent $320 million to produce
just 100,000 gallons of ethanol stands out as another black
mark against biomass.
downsides, reports NRDC, some policymakers seeking to promote
alternative fuels are proposing actions and policies that
would greatly increase the use of biomass. At the same time,
the group says, industry lobbyists are pushing to relax
biomass sourcing safeguards and “pushing to give industrial
biomass burning a ‘free pass’ on complying with
Clean Air Act mandates.”
Biomass can be
a part of the effort to cut back on fossil fuels, but only
if it is harvested and used in ways that reduce pollution,
cut emissions and protect forests. NRDC and other green
groups would like to see Congress impose stricter rules
to rein in soot, smog and greenhouse gases at biomass power
plants and pass measures that safeguard forests from deforestation
for biomass development.
Energy Agency; NRDC.