Understanding the Impacts of Climate Change on the United States

Dr. Virginia BurkettUSGS Chief Scientist for Global Change Research

U.S. Department of the InteriorU.S. Geological Survey

• The period of time over which we have instrumental records available is very short, and records only Earth’s recent warm climate over a period of relatively stable conditions.

a 65 million year Arctic climate synthesis

• Temperature and precipitation history• Past rates of climate change• History of the Greenland Ice Sheet• History of Arctic sea ice

• A sustained warming of 4° - 13°F over central Greenland will lead to the eventual melting of most of the Greenland Ice sheet.

• Arctic amplification has been a pervasive feature of the Earth’s climate system for at least the last 4 million years

IPC

C 2007

• The current rate of human-influenced Arctic warming is comparable to peak natural rates documented by reconstructions of past climates.

• The size and speed of summer sea ice loss seen over the past few years is highly anomalous relative to the previous few thousands of years.

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10°C increase in about a decade at end of Younger Dryas interval (YD)

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Abrupt Climate Change

Will climate response to future greenhouse warming be gradual or abrupt?

Abrupt Climate Change

Muir glacier, AK 1941 & 2004

Photo Credit: Molnia, USGS

Four types of abrupt change stand out in the geologic record as being so rapid and large in their impact that, if they were to recur, they would pose clear risks to society in terms of our ability to adapt.

1. Rapid change in glaciers, ice sheets, and hence sea level.

2. Widespread and sustained changes to the hydrologic cycle, primarily drought.

3. Abrupt change in the Atlantic Meridional Overturning Circulation (AMOC), a critical component of global climate, characterized by the northward flow of warm, salty water in the upper layers of the Atlantic Ocean.

4. Rapid release to the atmosphere of methane, a powerful greenhouse gas, trapped in permafrost and in ocean sediments.

(1) Ice sheets and sea level

(2) Drought

Rapid changes affecting the marginal regions of the Greenland and Antarctic ice sheets may mean more melting and higher sea level than previously predicted.

Climate models indicate that aridity in the southwestern U.S. will likely intensify and persist due to future greenhouse warming; if the model results are correct, this drying may have already begun.

Bamber, et al., 2007

Photo Credit: Jupiter Images

(3) Atlantic meridional overturning circulation (AMOC)

(4) Methane

A collapse of the AMOC is very unlikely in the 21st century, however, a reduction in strength of 25-30% is very likely.

An abrupt release of methane to the atmosphere this century is very unlikely. However, it is very likely that climate change will accelerate the pace of persistent emissions from hydrates and wetlands.

Kuhlbrodt et al., 2007

Photo Credit: Molnia, USGS

Ecosystem Thresholds

“The point at which there is an abrupt change in a quality, property, or phenomenon or where small changes in a driver may produce large responses in the ecosystem”. (Groffman et al, 2006)

Source: Brandon Bestelmeyer

1933 2003

Grasslands to shrublands . . . .

Key Drivers of Threshold-type Responses

Coastal Zones • Intense tropical storms• Sea level rise

• Summer SST increase (1°C)• Intense tropical storms

Coral ReefsCoral Reefs

Alaskan Ecosystems

Forests • Drought

• Fire• Pest and disease outbreaks

• Thaw of permafrost• Insects and wildfire• Loss of sea ice

Coastal Retreat, Alaska N. Slope

Blackwater National Wildlife Refuge, Chesapeake Bay, Maryland. Current land areas and potential inundation due to climate change

Sea Level Rise – Mid-Atlantic Region

Ocean Coasts

• It is virtually certain that erosion will dominate changes in shoreline position along the mid-Atlantic ocean coasts in response to sea-level rise and storms

• For higher sea-level rise scenarios, it is

very likely that some portions of the mid-Atlantic coast will undergo large changes which will depend in part on local geologic and oceanographic conditions

• Specifically, some barrier island coasts will likely cross a threshold and become prone to more rapid landward migration or segmentation

Impacts on Gulf Coast Transportation

Transportation Analysis Team

• Rail • Airports• Pipelines

• Highways and transit• Long range transportation

planning

• Emergency Management

• Ports and waterways

Federal Advisory Panel

Impacts on Gulf Coast Transportation

Relative sea level rise of 4 feet could permanently flood:• 24% of interstate miles, 28% of arterial miles• 72% of freight facilities at ports• 9% of the rail miles operated, 20% of the freight facilities• 3 airports

Key Drivers: Temperature, Precipitation, Runoff, Storms, Sea Level Rise

Relative sea level rise of 2 feet could permanently flood:• 19% of interstate miles, 20% of arterial miles• 64% of freight / 68% of non-freight facilities at ports

Unified Synthesis Product

Expected release April 2009