Geoscience Reference
In-Depth Information
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How do changes in climate affect the characteristics —(distribution, amount, intensity,
frequency, duration, type) of precipitation with particular emphasis on extremes of
droughts and floods? Increased temperatures and associated increases in lower
tropospheric water vapor, by making more water vapor available to storms, will very
likely increase the intensity of rains and snows, increasing risk of severe floods.
Changes in seasonality, shifts in monsoons, changes in snow-melt and runoff, and so on
are also part of this question which is elaborated on in the ''extremes'' science question.
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How do models become better and how much confidence do we have in global and
regional climate predictions of precipitation? A challenge to the Earth System science
community is to develop improved global models. Scientists are beginning to run
global climate models at sub-10-km resolution, resolving meso-scale weather including
the most extreme tropical storms. These need to be coupled to the ocean and land and
will require a new generation of parameterizations that better reflect what processes are
and are not resolved in such models. These models can potentially revolutionize our
ability to correct long-standing model biases, minimize the need for downscaling and
provide predictions of regional impacts and changes in extremes from months to
decades ahead. There is great need to quantify the uncertainty in precipitation
projections and predictions, especially at regional scales. Starting with improved
uncertainties in the climate observations of precipitation, new and improved
diagnostics must be developed to test the robustness of model predictions in different
regimes. Knowing the uncertainties is critical if predictions of the mean precipitation
and its distribution are to be used in local planning efforts.
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How do changes in the land surface and hydrology influence past and future changes in
water availability and security? While the land surface has small heat capacity and heat
moves slowly via conduction, the water flow and storage vary enormously. Land has a
wide variety of features, topography, vegetation cover and soil types and consists of a
mixture of natural and managed systems. Land plays a vital role in carbon and water
cycles, and ecosystems functions and services. Of particular need of attention is use of
realistic land surface complexity in hydrological models with all anthropogenic effects
included instead of a fictitious natural environment. This includes all aspects of global
change including water management, land-use and land-cover change and urbanization,
and their feedbacks to the climate system. There is a need to address terrestrial water
storage changes and close the water budget over land through exploitation of new
datasets, data assimilation, improved physical and biogeochemical understanding and
modeling skill across scales, from catchments to regional to global with links to the
entire hydrological cycle.
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How do changes in climate affect terrestrial ecosystems, hydrological processes, water
resources and water quality, especially water temperature? The ecosystem response to
climate variability and responsive vegetation must be included but is mostly neglected
in today's climate models. Cryospheric changes such as permafrost thawing, changes in
the extent, duration and depth of seasonal snowpacks, and changes in mountain glaciers
must also be included. How changes in vegetation affect the hydrological cycle and
climate in turn are vital. Feedbacks, tipping points and extremes are of particular
concern to all economic sectors and regions, globally. The scientific knowledge of
water cycle should enhance the evaluation of the vulnerability of water systems,
especially to extremes, which is vital for considerations of water and food security and
can be used to increase their resilience through good management practices and
governance.
