Hydrology BC ENV 3025
Water resources and climate change, global and in the Metro East
Coast Region
The Earth's climate system has undergone dramatic changes in the
past
- Rapid glacial/interglacial changes (Fig)(Fig)
- Observations of the recent past
- greenhouse gases (Fig)
- radiative forcing (2005, Fig)
- temperature, sea level, snow cover (Fig)
- phenomena and direction of trends (Table)
- regional temperature trends (Fig),
natural
versus anthropogenic
- "Most of the observed increase in global average
temperatures
since the mid-20th century is very likely due to the
observed increase
in anthropogenic greenhouse gas concentrations"
The IPCC (2007) has put considerable effort into predicting the
futures
- Projections
- global mean temperature projections (Fig)
under various emission (table)
scenarios
- regional predictions (Fig)
- projected patters of precipitation changes (Fig)
- prediction relevant to the water cycle (Fig):
- Snow cover is projected to contract. Widespread increases
in
thaw depth are projected over most permafrost regions
- Sea ice is projected to shrink in both the Arctic and
Antarctic under all SRES scenarios. In some projections,
arctic
late-summer sea ice disappears almost entirely by the latter
part of
the 21st century
- Based on a range of models, it is likely
that future tropical cyclones (typhoons and hurricanes) will
become
more intense, with larger peak wind speeds and more heavy
precipitation
associated with ongoing increases of tropical sea surface
temperatures.
There is less confidence in projections of a global decrease
in numbers
of tropical cyclones. The apparent increase in the
proportion of very
intense storms since 1970 in some regions is much larger
than simulated
by current models for that period
- Extratropical storm tracks are projected to move poleward,
with consequent changes in wind, precipitation and
temperature
patterns, continuing the broad pattern of observed trends
over the last
half-century.
- There is an improving understanding of projected patterns
of
precipitation. Increases in the amount of precipitation are
very likely in high latitudes, while
decreases are likely in most
subtropical land regions (by as much
as about 20% in the A1B scenario in 2100), continuing
observed patterns
in recent trends.
Local predictions (NYC DEP)
Southwestern United States (Seager et al., 2007)
- P-E changes for the 2021-2040 period minus 1950-2000 (contour
lines,
Fig)
- P-E changes over American Southwest (Fig)
- Differences between models (Fig)
Exercises
The Global
Historical
Climatological
Network Data set allows us to look at historical temperature
and
precipitation trends. Select a region using the mapping tool and
then
look for trends in temperature and precipitation.
What can you say about the future
combined
effects of the precipitation patterns and temperature
patterns
together
on the region of your choice (if you extrapolate the existing
trends)?
Resources
