10/05/02 -- Land Use Rivals Greenhouse Gases in Changing Climate

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FOREST CONSERVATION NEWS TODAY

Land Use Rivals Greenhouse Gases in Changing Climate

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October 5, 2002

OVERVIEW & COMMENTARY by Forests.org

Climate change scientists and policy makers have primarily been focusing upon

how heat-trapping gases like carbon dioxide are altering our global climate. A

new NASA-funded study suggests human-caused land-use changes may ultimately be

the major factor contributing to climate change. The paper was published in a

recent issue of the Philosophical Transactions of the Royal Society of London

and the NASA press release on this important study can be found at:

http://www.gsfc.nasa.gov/topstory/20020926landcover.html

"Our work suggests that the impacts of human caused landcover changes on climate

are at least as important, and quite possibly more important than those of

carbon dioxide," said Roger Pielke, an atmospheric scientist at Colorado State

University. The study concludes that changes in the land surface such as urban

sprawl, deforestation and reforestation, and agricultural and irrigation

practices strongly affect regional surface temperatures, precipitation and

larger-scale atmospheric circulation. The study contends “that human-caused

land surface changes in places like North America, Europe, and southeast Asia,

redistribute heat regionally and globally within the atmosphere and may actually

have a greater impact on climate than that due to anthropogenic greenhouse gases

combined.”

For example, deforestation and reforestation alter the amount of sunlight the

land absorbs, and the amount of moisture it releases. Amazonian deforestation

may have a large and long lasting impact on climate. Continued penetration of

the Amazon and the Planet’s other remaining large and contiguous forest

ecosystem engines for oil drilling has a double whammy – as forests carbon

stores are released and global addiction to fossil fuels is perpetuated.

Global ecological sustainability - indeed survival of most species including our

own - depends upon protecting, conserving and restoring natural habitats, and

eliminating emissions of greenhouse gases. The threats posed by crazy

megalomaniac terrorists, a tinpot Iraqi dictator and an imperial U.S. presidency

pale in comparison to the global threats to security posed by looming ecological

overshoot and imminent collapse. Global land use and climate policy, along with

water scarcity and oceanic declines, are by far the greatest threats to the

community of humanity. If the goal of humanity is just, equitable, free, secure

and sustainable societies; they deserve at least equal billing and funding as

military security issues.

g.b.

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ITEM #1

Title: Land Use Rivals Greenhouse Gases in Changing Climate

Date: October 2, 2002

Byline: Cat Lazaroff

WASHINGTON, DC, October 2, 2002 (ENS) - Changes in land use may rival greenhouse

gases in their contributions to global warming, suggests a new international

study. The report details the effects of urban sprawl, deforestation and

agricultural practices on regional surface temperatures, rainfall patterns and

atmospheric circulation, arguing that these land surface changes may have more

impact on climate than greenhouse gas emissions.

Most climate change studies have focused on how heat trapping gases like carbon

dioxide (CO2), released by human activities such as the burning of fossil fuels,

are warming the global climate. However, other human activities which cause

changes in land surfaces and vegetation may be even more important, say the

authors of a recent study.

The study argues that human caused land surface changes in places like North

America, Europe and southeast Asia redistribute heat within the atmosphere both

regionally and globally, and may actually have a greater impact on climate than

that due to all greenhouse gases released by human activities.

"Our work suggests that the impacts of human caused landcover changes on climate

are at least as important, and quite possibly more important than those of

carbon dioxide," said Roger Pielke, an atmospheric scientist at Colorado State

University.

"Through landcover changes over the last 300 years, we may have already altered

the climate more than would occur associated with the radiative effect of a

doubling of carbon dioxide," added Pielke, who is lead author of the new study

appearing in the August 2002 issue of "Philosophical Transactions: Mathematical,

Physical & Engineering Sciences," a journal of The Royal Society of London.

Pielke and his colleagues noted that if CO2 emissions continue at current rates,

atmospheric CO2 concentrations are expected to double by 2050. At the same time,

land surface uses will continue to change.

Different land surfaces influence how the sun's energy is distributed back to

the atmosphere. For example, if a rainforest is removed and replaced with crops,

there is less transpiration, or evaporation of water from leaves. Less

transpiration leads to warmer temperatures in that area.

On the other hand, if farmland is irrigated, more water is transpired and also

evaporated from moist soils, which cools and moistens the atmosphere, and can

affect precipitation and cloudiness.

Forests may influence the climate in more complicated ways than previously

thought, the authors found. For example, in regions with heavy snowfall,

reforestation or the growth of new forests would cause the land to reflect less

sunlight, meaning that more heat would be absorbed. This could result in a net

warming effect, even though the new trees would remove CO2 from the atmosphere

through photosynthesis during the growing season.

Reforestation could increase also transpiration in an area, putting more water

vapor in the air. Water vapor in the troposphere, the lowest densest part of the

earth's atmosphere, is the biggest contributor to greenhouse gas warming, the

researchers said.

Local land surface changes can also influence the atmosphere in far reaching

ways, much like regional warming of tropical eastern and central Pacific Ocean

waters known as El Niño. El Niño events create moist rising air, thunderstorms

and cumulus clouds, which in turn alter atmospheric circulations that export

heat, moisture, and energy to higher latitudes.

Tropical land surface changes should be expected to play a greater role on

global climate than El Niño, the researchers argue, because thunderstorms prefer

to form over land. The large area where tropical land uses are changing far

exceeds the relatively small area of water responsible for El Niño, the authors

explain.

However, the impacts of land use changes are often harder to detect because they

are permanent, while El Niño's effects are temporary and dramatic.

Pielke and his colleagues propose a new method for comparing different, human

influenced agents of climate change in terms of the way that they redistribute

heat over land and in the atmosphere.

This heat redistribution would be stated in terms of watts per meter squared, or

the amount of heat associated with a square meter area. For example, if a

flashlight generated heat of one watt that covers a square meter, then the heat

energy emitted would be one watt per meter squared.

Using a single unit of measurement may open the door to future work that more

accurately represents human caused climate change, the authors said.

The study was funded by grants from the U.S. National Science Foundation and the

National Aeronautics and Space Administration.

ITEM #2

Title: Farming, logging, development affect climate, too

Date: October 3, 2002

Byline: Richard Stenger (CNN)

(CNN) -- Cutting trees, building cities and growing crops have profound effects

on the climate in addition to human activities that release greenhouse gases, a

new NASA study reports.

Land surface disturbances influence everything from temperature, precipitation,

atmospheric circulation and how much solar heat bounces off the planet.

Concentrated development, in particular in North America, Europe and Southeast

Asia, disperses enough heat into the atmosphere to rival the effect of all

greenhouse gas emissions combined, according to atmospheric scientists.

"Our work suggests that the impacts of human-caused land cover changes on

climate are at least as important, and quite possibly more important, than those

of carbon dioxide," said Roger Pielke Sr. of Colorado State University in Fort

Collins.

Carbon dioxide is the primary culprit among numerous heat-trapping gases caused

by human activity thought to contribute to global warming.

"Through land cover changes over the last 300 years, we may have already altered

the climate more than would occur associated with the ... effect of a doubling

of carbon dioxide," Pielke said in a statement this week.

If current trends continue, carbon dioxide concentrations in the atmosphere will

double within 50 years.

Scientists predict that the added greenhouse gases could push the global

temperature up several degrees by the end of this century, causing major changes

in regional weather patterns.

Pielke and colleagues, who conducted the study for NASA's Earth Observing System

Project Office and the National Science Foundation, said the type of land

surface affects how it redistributes solar energy into the atmosphere.

For instance, if farmers replace forests with crops, less water evaporates from

leaves, which contributes to hotter temperatures in that area, they said.

And in places with dwindling snow or ice cover, whether because of retreating

glaciers or reforestation, the land reflects less sunlight and absorbs more

heat, leading to hotter temperatures.

The net effects are complex and sometimes seem contradictory. For example,

compared with non-irrigated land, more water evaporates from irrigated fields,

which cools and moistens the nearby air.

Yet on a larger scale, atmospheric water vapor contributes greatly to greenhouse

gas warming.

The scientists propose a new method to predict climate change, which factors in

how different kinds of land forms absorb, reflect or distribute heat.

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