Climate Change - 4.26.06

STATEMENT OF

DR. THOMAS R. ARMSTRONG

PROGRAM COORDINATOR,

EARTH SURFACE DYNAMICS PROGRAM

U.S. GEOLOGICAL SURVEY

U.S. DEPARTMENT OF THE INTERIOR

PROJECTED AND PAST EFFECTS OF CLIMATE CHANGE: A FOCUS

ON MARINE AND TERRESTRIAL ECOSYSTEMS

BEFORE THE

COMMITTEE ON COMMERCE, SCIENCE AND TRANSPORTATION

SUBCOMMITTEE ON GLOBAL CLIMATE CHANGE AND IMPACTS

UNITED STATES SENATE

April 26, 2006

Mr. Chairman and Members of the Subcommittee, thank you for the opportunity to participate in this hearing on climate change and its effects on terrestrial and marine systems. My name is Tom Armstrong, and I am the Program Coordinator for the Earth Surface Dynamics Program at the U.S. Geological Survey (USGS). I also represent USGS and the Department of the Interior as a member of the U.S. Climate Change Science Program and the Climate Change Working Group of the Arctic Monitoring and Assessment Program.

The USGS strives to understand how the earth works and to anticipate changes in how the earth functions. To accomplish this, USGS science aims to understand the interrelationships among earth surface processes, ecological systems, and human activities. This includes understanding current changes in the context of pre-historic and recent earth processes, distinguishing between natural and human-influenced changes, and recognizing ecological and physical responses to changes in climate.

We conduct scientific research in order to understand the likely consequences of climate change, especially by studying how climate has changed in the past and using the past to forecast responses to shifting climate conditions in the future. My testimony today will address three major sets of challenges:

1. Distinguishing natural from human-influenced climate change;

2. Understanding ecological and physical responses to climate change, and predicting the related impacts of these responses on climate; and

3. Effectively conveying cutting-edge climate science to policy-makers, decision-makers, and the public.

I will conclude my testimony with a brief discussion of the state of our understanding of climate science and how this provides a roadmap to our future understanding of long-term climate change and its impact on people, natural resources, and the Earth.

Distinguishing natural from human-influenced climate change

In a statement on behalf of the Administration to the Senate in July, 2005, Dr. James R. Mahoney, now former Assistant Secretary of Commerce for Oceans and Atmosphere, and Director of the U.S. Climate Change Science Program, stated, “We know that an increase in greenhouse gases from the use of energy from fossil fuels and other human activities is associated with the warming of the Earth's surface.” This statement underlies the growing public debate on climate change: are humans and their activities the driving force behind global warming? The scientific community is largely in agreement that human activity in the 20thand 21stcenturies has enhanced greenhouse gas concentrations in the atmosphere, and these added gases have an effect on global temperatures and climate. Climate change is also a natural, continuous, inevitable Earth process that is influenced by many forces, one of which is the concentration of both naturally-emitted and human-induced greenhouse gases in the atmosphere. Many other forces also control climate change, including cyclical changes in solar radiation, movement of the Earth's tectonic plates, oscillations in ocean temperatures and ocean currents, and the positions and magnitudes of meteorological entities such as high, low, and convergent zones. In fact, natural climate change has occurred on a regular basis on this planet for at least the last 800,000 years and possibly much longer. Paleoclimate research has shown that the Earth has experienced several episodes of global warming in this timeframe during which air temperatures and levels of CO2increased in ways comparable to the present day changes, although the ice record indicates that the current concentrations of CO2in the atmosphere are unprecedented during human existence. Understanding the science of natural variability in climate is essential to the formation of effective policy regarding the mitigation of or adaptation to climate change, both human and natural.

One of the major challenges facing the climate science community is distinguishing natural climate change from that imposed upon the natural system through human activities. This science must also develop an effective understanding of the consequences of the human-induced component. The science we conduct in order to understand both the human component of climate change and its potential impacts on the natural climate system is known as climatology; paleoclimatology looks into the prehistoric past of the Earth in order to determine how climate change occurred prior to human activity. Through paleoclimate studies, scientists have been able to determine that climate changes naturally, and that there indeed are natural climate cycles that have occurred regularly, and in a predictable fashion, over at least the last 800,000 years of Earth history.

By studying various parameters, or proxies, in the prehistoric record, such as tree-rings, ice-cores, and fossil pollen records, scientists at USGS and elsewhere have been able to develop a detailed record of climate change, including changes in temperature and atmospheric CO2concentrations over the last several hundred thousand years (Figure 1). This record shows that natural climate change predates human influence and is generally cyclical in nature, with long-term periods of global cooling and glaciation (40,000 to 50,000) years long, punctuated by shorter-term periods of global warming and deglaciation (10,000 to 15,000 years in duration). The general consensus among climate scientists is that we are within a new interglacial period with related global warming.