USGS identifier

Science Goals

Goal 4--Anticipate the environmental impacts of climate variability

Climates are constantly changing, and understanding and assessing the impacts of climate change are some of the most significant and controversial issues facing scientists and society today. For example, the 20th century instrumental record suggests that global warming is occurring, but the driving force for this change is not understood. Is this apparent warming part of normal climate variability, does it reflect increasing levels of atmospheric greenhouse gases due to human activities, or are both factors involved? Further complicating this question are paleoclimatic data suggesting that climate may undergo abrupt global-scale shifts over a matter of a decade or two, rather than smooth, gradual transitions over longer periods. Regardless of the cause of climate change, the environmental and economic consequences of continued warming are enormous. Densely populated coastal zones may be inundated and (or) face large-scale erosion as sea level rises (see Highlight 9); some agricultural regions may face significant droughts; and other areas may face increased frequency of floods or hurricanes.

Defining the range and rates of natural climate variability is the key both to assessing the historic human influence on climate and to predicting the effects of climate changes. The instrumental record of climate is restricted largely to the last hundred years and is grossly inadequate to understand the dynamics of the modern climate. The only way to extend this meager climate record is through continued detailed paleoclimatological analysis of the historic and geologic past. The USGS is working to help define the magnitude, extent, and impact of past climate change as well as the frequency of climate variability. Specifically, there are two areas in which the GD will assume a leadership role in the U.S. Global Change Program: (1) continental- and regional-scale reconstruction of key past climates, using a combination of terrestrial and marine paleoclimate records, and (2) modeling or forecasting the effects of climate changes on landscapes of the United States, including effects on both geomorphic processes (see Highlight 10) and vegetation distribution (see Highlight 11). The GD will make this information available so that it can be considered in formulating local and national land-use decisions, as well as in national and global economic policies responding to ongoing climate change.


National- and regional-scale reconstructions of past climates (precipitation and temperature) and past environments (landforms and vegetation).
The GD will provide reconstructions for both Holocene (the past 10,000 years) and pre-Holocene time periods to compare with results from atmospheric general-circulation models.

Quantitative regional assessments of vulnerability to climate change and likely environmental impact scenarios.
Examples of scenarios the GD will prepare include the effect of precipitation changes on fluvial erosion and landslide hazard, the impact of sea-level changes on coastal erosion and inundation, the impact of drought-induced remobilization of dune sand on crop land and atmospheric dust levels, the impact of precipitation changes on ground- and surface-water supplies, and the shift in distribution of plant species due to climate change.

High-resolution time series of past climatic conditions.
The GD will prepare series particularly for (but not limited to) the Holocene, using key climate proxy data, with emphasis on the terrestrial record. Such efforts will be conducted in order to document the natural range of climate variability and to identify the frequency of extreme climatic conditions, such as droughts or extended periods of very high precipitation.

National and regional maps showing possible early warning indicators of climate change.
Examples of indicators that the GD might map include areal and volumetric changes in glaciers, shifts in vegetation distribution, extent and depth of permafrost, extent and magnitude of atmospheric dust flux and dust storms, and distribution and degree of activity of dune sand.

Strategic Actions

Reconstruct key past climates under a range of conditions and compare these to atmospheric general-circulation model results.
These reconstructions will emphasize warm climates of the past but will also include some studies of cold climates and the transitions between past climate states. Highly interdisciplinary paleoclimate studies of both terrestrial and marine records and frequent interaction with the climate-modeling community will be required.

Identify areas highly sensitive to climate variability and determine critical thresholds of temperature and precipitation changes that can induce vegetation and geomorphic changes.
Changes in highly sensitive areas such as arid zones and Arctic regions can result in extensive fluvial erosion, landsliding, dune reactivation, and enhanced coastal erosion. The GD will establish quantitative measures of vulnerability to climate change and incorporate these into predictive models of landscape and ecosystem evolution resulting from probable future climate changes.

Refine data on the magnitude and frequency of climate and paleoecological changes during the Holocene to higher resolution.
High-resolution records are required for sedimentation, landforms, pollen, and stable isotopes in fossil materials, and obtaining them will necessitate developing and exploiting cutting-edge Holocene dating techniques. This effort will also include developing and testing new climate proxies available from the geologic record.

Collaborate with other agencies to initiate and expand long-term baseline mapping of key climate-change indicators.
The GD will collaborate with other Federal agencies, particularly NASA and the National Oceanic and Atmospheric Administration (NOAA), and foreign institutions to map key climate-change indicators, such as glaciers, vegetation, permafrost, and dune sand. Such efforts will likely include extensive use of remote-sensing and geographic information system (GIS) techniques.

Study the fundamental processes and key biogeochemical cycles governing climate change and climate-related hazards, with emphasis on the terrestrial domain.
One process affecting the carbon cycle and influencing climate change may be the release of methane by destabilization of natural carbon storage reservoirs. This destabilization can result from melting of permafrost or depressurization of sea-floor hydrates due to a drop in sea level.

<----- Back to Contents || Back to Goal 3 || Continue to Goal 5 ----->

This page is <>
Maintained by L. McElroy
Last updated 04.08.98