Wall Street History
The National Oceanic and Atmospheric Administration recently
came out with a report on extreme weather and how we can
expect it to become more common. Should this pan out over the
coming decades, it of course has major economic implications.
Ergo, it’s far from a stretch to write of this topic for this column.
From NOAA’s report:
Weather and climate extremes affect all sectors of the economy
and the environment, including human health and well-being.
During the period 1980-2006, the U.S. experienced 70 weather-
related disasters in which overall damages exceeded $1 billion at
the time of the event. Clearly, the direct impact of extreme
weather and climate events on the U.S. economy is substantial.
There is scientific evidence that a warming world will be
accompanied by changes in the intensity, duration, frequency,
and geographic extent of weather and climate extremes.
Changes in extremes are already observed to be having impacts
on social, economic and natural systems, and future changes
associated with continued warming will present additional
The impacts of changes in extremes depend on both changes in
climate and ecosystem and societal vulnerability. Vulnerability
is shaped by factors such as population dynamics and economic
status, as well as developing and utilizing adaptation measures
such as appropriate building codes, disaster preparedness, and
water use efficiency. Some short-term actions taken to lessen the
risk from extreme events can lead to increases in vulnerability to
even larger extremes. For example, moderate flood control
measures on a river can stimulate development in a now “safe”
floodplain, only to see those new structures damaged when a
very large flood occurs.
Within a changing climate system, some of what are now
considered to be extreme events will occur more frequently (e.g.,
heat waves) and some less frequently (e.g., cold snaps). More
frequent extreme events occurring over a shorter period reduce
the time available for recovery and adaptation. In addition,
extreme events often occur in clusters. The cumulative effect of
compound or back-to-back extremes has far larger impacts than
the same events spread out over a longer period of time. For
example, heat waves, droughts, air stagnation, and resulting
wildfires often occur concurrently and have more severe impacts
than any of these alone.
What Changes Have Already Occurred?
Many extremes and their associated impacts are now changing.
--Most of North America is experiencing more unusually hot
days and nights and fewer unusually cold days. The last 10 years
have seen fewer severe cold waves than any other 10-year period
in the historical record, which dates back to 1895. The number
of heat waves has also been increasing since 1950.
--There has been a decrease in frost days and a lengthening of the
frost-free season over the past century.
--Extreme precipitation episodes (heavy downpours) have
become more frequent and intense and now account for a larger
percentage of total precipitation.
--Droughts are becoming more severe in some regions.
--Atlantic tropical storm and hurricane destructive potential has
increased substantially since about 1970.
--Storm tracks have shifted northward in both the North Atlantic
and North Pacific over the past fifty years. The strongest cold
season storms are becoming even stronger in the North Pacific.
Why Have These Changes Occurred?
As the climate has warmed, primarily due to human activities,
we have also seen a variety of changes in extremes. Some
examples of extremes that have an identifiable cause.
--Human-induced warming has likely caused much of the
average temperature increase in North America over the past
fifty years and, consequently, changes in temperature extremes.
For example, the effect of human-induced emissions of
greenhouse gases has been associated with the very hot year of
2006 in the U.S.
--Heavy precipitation events averaged over North America have
increased over the past 50 years, consistent with the observed
increases in atmospheric water vapor, which have been linked to
human-induced increases in greenhouse gases.
--It is likely that the human-induced increase in air temperatures,
and the associated increase in evaporation potential over land,
are already contributing to droughts that are longer and more
--It is very likely that the human-induced increase in greenhouse
gases has contributed to the increase in sea surface temperatures
in the hurricane formation regions. Because there is a strong
statistical connection between Atlantic tropical sea surfaces
temperatures and Atlantic hurricane activity, this suggests a
human contribution to recent hurricane activity (a confident
assessment will require further study).
--Human influences on changes in sea-level pressure patterns
have been detected over the Northern Hemisphere and this
affects the location and intensity of cold season storms.
How Will Extremes Change
Projected continued warming of North America has direct
implications for the occurrence of extreme weather and climate
events. For example, climate models indicate that many
currently rare extreme events will become more commonplace.
For a mid-range scenario of future greenhouse gas emissions, a
day so hot that it is currently experienced only once every 20
years would occur every three years by the middle of the century
over much of the continental U.S. and every five years over most
of Canada. By the end of the century, it would occur every other
year or more.
--Future changes in extreme temperatures will generally follow
changes in average temperature. Abnormally hot days and nights
and heat waves are very likely to become more frequent. Cold
days and cold nights are very likely to become much less
frequent. The number of days with frost is very likely to
--Sea ice extent is expected to continue to decrease and may even
disappear entirely in the Arctic Ocean in summer in the coming
decades. This increases extreme coastal erosion in Arctic Alaska
and Canada due to the increased exposure of the coastline to
strong wave action.
--On average, precipitation is likely to be less frequent but more
intense, and precipitation extremes are very likely to increase.
--In the future, droughts are likely to become more frequent and
severe in some regions, leading to an increased need to respond
to reduced water supplies, increased wildfires, and various
ecological impacts. These regions include the U.S. Southwest
and parts of Mexico.
--For North Atlantic and North Pacific hurricanes, it is likely that
rainfall and wind speeds will increase in response to human-
caused warming. Analyses of model simulations suggest that,
for each 1.8-degree F increase (1 C.) in tropical sea surface
temperatures, core rainfall rates will increase by 6 to 18% and
the surface wind speeds of the strongest hurricanes will increase
by about 1 to 8%.
--In the future, there are likely to be more frequent strong cold-
season storms in both the Atlantic and Pacific basins, with
stronger winds and more extreme wave heights.
Source: National Oceanic Atmospheric Administration, noaa.gov
Note: NOAA was only able to utilize data through 2006 for their
report but clearly the catastrophic Midwest rains and tornadoes
from this current season play into the above theories.
Wall Street History returns July 11.