Because
there are so many variables involved in forecasting weather
and climate, sophisticated models have been developed to
produce scenarios of potential or likely events. While these
models have improved forecasting, accurate longer term and
even annual and seasonal forecasts remain elusive.
For weather forecasts,
eleven to fourteen days in the future is generally regarded
as limit for accurate forecasts, with uncertainty growing
the further out a forecast goes. When it comes to forecasting
climate in the months, years and decades ahead, there are
many challenges in accurately predicting what the future
holds. When an ENSO event-- either the warm pulse of El
Niño or cool pulse of La Niña-- is identified,
certain general predictions based on probability can be
made at a regional level. But not all regions are impacted
by ENSO, and even when forecasts are accurate, they are
not always clearly communicated to or by the media, nor
are they necessarily used by those they are intended to
benefit.
Currently, one of the most important and both scientifically
and politically controversial
climate concerns is
that of Global warming. The
instrumental temperature record of the past 150 years shows
that overall the Earth has warmed close to 0.5 degrees C
or 0.9 F., and evidence suggests that the cause is the burning
of fossil fuels which release carbon and other greenhouse
gases into the atmosphere. Regional assessments, such as
the United States Global Change Research Program's report,
"The
Potential Consequences of Climate Variability and Change-
US National Assessment"
acknowledge that regional impact will likely be varied and
that not all regions will necessarily become drier and hotter.
There are skeptics within the scientific community who question
the extent and causes of global warming and how future projections
are modeled, such as Dr. William Gray who believes the hydrologic
cycle acts as a thermostat on the Earth's climate that will
prevent a runaway greenhouse effect.
Generally, however, there is consensus that greenhouse gases
are building up, that the cause is primarily the burning
of fossil fuels, and that change is occurring in the Earth's
climate system. If the
forecasts by IPCC scientists of 2.5–10.4°F by 2100
are true, entire species and biomes are may become extinct
on a mass scale. Studies
of vegetation changes in North America after the warming
at the end of the last Ice Age may provide insight into
what is in store in the next 100-200 years.
As
to what actions should be taken to address the buildup of
greenhouse gasses and land-use changes impacting the global
system and what can be done to mitigate against climate
variability, there
remains considerable debate among scientists, policy makers,
politicians and industrialists. Some climate scientists,
such as Richard Alley,
note that models of past and future climate change tend
to smooth out actual variations, and that the real-world
climate system tends to be more extreme than models show.
Moreover, abrupt climate changes
have occurred in the past that models can never get exactly
right.
For a visualization
of how climate change can impact a particular region,view
an animation (1250kb) showing changes and potential
changes
in glaciers and vegetation from
1850 to 2100 from Predicting
the Impact of Climate Change on Glacier and Vegetation Distribution
in Glacier National Park to the Year 2100.
