A Word of Caution


A new look at the long-term and short-term effects of vast fires in northern forests shows that the blazes may speed up global warming at first, then help cool things off over the long haul.

By studying changes on the ground from a 1999 fire in Alaska, researchers have found that the largest warming effect lasts about a year, but the cooling — caused by sunlight reflecting off snow and new plant growth — lasts another 80 years.

The upshot is that overall, the net contribution to global warming by large fires in these "boreal" forests may be negligible.

"The study shows there’s a good chance that (these fires) will not have an effect on global warming," confirmed James Randerson, an Earth system science professor at the University of California at Irvine. He and his colleagues have published their findings in the Nov. 17 issue of the journal Science.

When a large, catastrophic fire burns in a boreal forest, it generally consumes everything and leaves the blackened stumps of trees. In the process the fires release a pulse of carbon dioxide and methane into the atmosphere.

Those two greenhouse gases last for decades, contributing to the overall rise in greenhouse gases caused primarily from the burning of fossils fuels.

The fires have also been blamed for depositing wind-borne soot on Arctic sea ice and Greenland’s glaciers — causing them to absorb more energy from the sun and melt, Randerson explains.

It turns out, however, that all the bare, snow-covered ground that was once shaded by dark conifers reflects a lot more sunlight back into space than an unburned, mature evergreen forest, report Randerson and his colleagues. That means it's cooler there than before the fire.

The same burned lands also recapture a lot of carbon dioxide as new plants — usually willows and other deciduous colonizers — sprout and grow. So over the decades, there’s a big cooling effect after a fire that is drawn out by the very slow growth of the dominant spruce trees of those forests.

The new study demonstrates just how important it is to look beyond the immediate effects of a fire or other changes to the vegetation, to tease out how they ultimately interact with climate.

"We have to look at the big picture to get the whole balance," said Earth system researcher Robert Jackson of Duke University. "If you just look at the short-term there’s no doubt that fires contribute to warming."

Since global warming is a long-term process, it makes more sense to look at forest fires through the same lens.

"It’s good news through the lens of climate change," said Jackson, because it means the fires are probably not part of the global warming problem. On the other hand, it also means that, once again, the main culprit in warming is the burning of fossil fuels.

"Land use change matters," Jackson acknowledged, "but it still matters what comes out of your tailpipe."

New research on the sun's contribution to global warming is reported in Astronomy & Geophysics. By looking at solar activity over the last 11,000 years, British Antarctic Survey (BAS) astrophysicist, Mark Clilverd, predicts that the sun's contribution to warming the Earth will reduce slightly over the next 100 years.

This is a different picture to the last century when solar flares, sunspots and geomagnetic storms, increased in number. This rise is simultaneous with emissions of greenhouses gases and an estimated increase in solar heat output, which together have warmed the Earth's temperature by a global average of 0.7 degrees centigrade.

The solar contribution to the increase is variously estimated to be around 4 - 20% leaving greenhouse gases to make up the remaining 80%. Clilverd and colleagues conclude that solar activity is about to peak and predict less activity in the next 100 years, with the occurrence of space storms likely to decline by two thirds. Their assumption is that the solar heat output will decline slightly accordingly.

Clilverd examined data from sun spot activity, geomagnetic storm indices and looked at the variation of atmospheric radiocarbon derived from studies of tree rings and marine sediments to make his predictions.

He says, "This work is speculative and relies on the idea that the sun shows regular cycles of activity on timescales of 10 – 10,000 years and that its heat output and activity are related. But we believe the work is well grounded and the effect of solar activity on Earth's environmental system will not increase in the way it has during the last century. We should take this into account when trying to understand the impact of human activity on our climate system."

Although solar activity may reduce in 2100, Clilverd predicts it will return to its current levels by 2200.

Clilverd continues, "This research is important for understanding the severity and impact of climate change in coming centuries. As noted by Intergovernmental Panel on Climate Change in the Third Assessment Report, published in 2001, anthropogenic emissions of greenhouse gases are highly likely to cause warming of the Earth, but factors such as solar variability could amplify or subdue the effect."

The ozone layer, which protects all life from ultraviolet (UV) radiation, is being destroyed by release of chlorofluorocarbons (CFCs) into the atmosphere. The widening holes in the ozone layer allow in more UV rays, which can cause skin cancers, cataracts, and immune system damage. UV rays are detrimental to pollination, seed production, and marine life food supplies as well.

Ice sheets in the Arctic Ocean have receded to record lows, and Antarctic glaciers are melting at an unprecedented rate, causing sea levels to rise and indigenous wildlife to lose its habitat.

Nearly 90% of the permafrost in the Arctic could melt by 2100, which would not only extinguish wildlife, but also release an estimated 400 billion tons of methane, now trapped in the frozen soil, into the atmosphere, dramatically speeding up global warming.

Rising ocean levels could eventually cause worldwide flooding of coastal areas, forcing people and wildlife to migrate inland. Many experts believe global warming is behind the upswing in hurricane activity, and they also predict global warming will cause a dramatic increase in excessive precipitation in some areas and severe drought in others, resulting in floods, crop failures, and a rising number of forest fires and land slides.

Many of the world's most knowledgeable climate-change scientists forecast that the earth's temperature will rise from 1.44 to 6.3º F by the year 2100 if we don't take steps to reduce greenhouse gases. An increase of 1 to 3.6º F will occur even if we do act, because many gases have already been released.

Using an arsenal of ground-based radars, optical telescopes and forensic spacecraft observations, the NASA Orbital Debris Program Office estimates that 19,000 objects larger than 10 centimeters in diameter are known to exist. But the estimated population of particles between 1 and 10 centimeters is 500,000 and the number of particles smaller than 1 centimeter probably exceeds tens of millions, say scientists.

One particular study estimated that there are four million pounds of space junk orbiting in low-Earth orbit and any one of the pieces could potentially threaten spacecraft, the lives of astronauts, or any number of the spacecraft studying changes in our planet and atmosphere. And the debris that could potentially threaten the lives or the viability of a space mission need only to be the size of a raisin. As an example of the hazard, a tiny speck of paint from a satellite once dug a pit in a space shuttle window nearly a quarter-inch wide.

The good news is that most space junk is located between 550 and 625 miles above the Earth — the International Space Station flies in orbit at 250 miles above Earth, while space shuttles usually only reach about 375 miles high. The bad news, however, is that a recent NASA study forecast a ten-fold increase in the probability of collision with debris over the next 200 years.

What makes the 21st century problem of space junk particularly intractable is that it will likely get worse before it gets better. Many orbital debris analysts point out that current forecasts may not give a complete picture as they assume no increase in the rate of space expeditions. Current predictions were also made prior to the 2007 intentional destruction of a Chinese weather satellite. The Chinese ASAT test deposited more than 2,300 pieces of debris larger than 10 centimeters into some of the most heavily used orbits where the world’s weather and climate monitoring satellites reside.

The satellite breakup and resulting debris cloud was “the most prolific and serious fragmentation in the course of 50 years of space operations,” according NASA’s Nicholas Johnson, Chief Scientist for Orbital Debris.

Weeden says that up until now, the debris mitigation process has been focused mainly on the technical aspects, but more and more attention is now being paid to the legal dimensions of space debris. A first step towards this end was the recent establishment of the United Nations Space Debris Mitigation guidelines.

“At some point we will need to actively remove debris from orbit. Fortunately, new studies are showing that removing as few as five or six objects per year could stabilize the debris population over the long term,” said Weeden.

“The big question right now,” added Weeden, “is which objects to remove first and what is the best method to do so.”

      This is why we need to ban plastic bags as soon as possible and make it mandatory that people bring their own reusable bags to the store. San Francisco did it. A city in Maryland did it. The entire Whole Foods chain did it. The western Indian state of Maharashtra did it. In fact, Iceland did it. Enough is enough – everyone needs to do it.