Saturday, March 16, 2013

Risks from climate change

I've been focusing on the more spectacular and fast-acting risks, from meteor strikes and other natural disasters to the stock market here lately, which means I've been ignoring the usual long-term problems of pollution and resource depletion and their consequences, such as climate change. Time to remedy that.

I begin with the following from Nature via Scientific American, which was the big climate news of last week.

Global Average Temperatures Are Close to 11,000-Year Peak By the end of this century, Earth is set to get hotter than at any time since the last ice age By Sid Perkins and Nature magazine March 8, 2013
Global average temperatures are now higher than they have been for about 75% of the past 11,300 years, a study suggests. And if climate models are any indication, by the end of this century they will be the highest ever since the end of the most recent ice age.

Instrumental records of climate extend back to only the late nineteenth century. Beyond that, scientists depend on analyses of natural chronicles such as tree rings and isotope ratios in cave formations.

But even these archives have their limits: many detailed reconstructions of climate, particularly of temperature, apply to only limited regions or extend back at most a couple of millennia, says Shaun Marcott, a climate scientist at Oregon State University in Corvallis.
More climate news over the jump.

ScienceNOW via Wired: Recent Global Warming Slowed by Volcanoes By Sid Perkins, ScienceNOW
Global average temperatures have been rising in recent years, but not as much as they might have, thanks to a series of small-to-moderate-sized volcanic eruptions that have spewed sunlight-blocking particles high into the atmosphere. That’s the conclusion of a new study, which also finds that microscopic particles derived from industrial smokestacks have done little to cool the globe. 
Between 2000 and 2010, the average atmospheric concentration of carbon dioxide — a planet-warming greenhouse gas — rose more than 5%, from about 370 parts per million to nearly 390 parts per million. If that uptick were the only factor driving climate change during the period, global average temperature would have risen about 0.2°C, says Ryan Neely III, an atmospheric scientist at the University of Colorado, Boulder. But a surge in the concentration of light-scattering particles in the stratosphere countered as much as 25% of that potential temperature increase, he notes.
Scientific American: Clearing Forests May Transform Local—and Global—Climate
Researchers are finding that massive deforestation may have a profound, and possibly catastrophic, impact on local weather
By Judith D. Schwartz
March 4, 2013
In the last 15 years 200,000 hectares of the Mau Forest in western Kenya have been converted to agricultural land. Previously called a “water tower” because it supplied water to the Rift Valley and Lake Victoria, the forest region has dried up; in 2009 the rainy season—from August to November—saw no rain, and since then precipitation has been modest. Whereas hydropower used to provide the bulk of Kenya’s power ongoing droughts have led investors to pull out of hydro projects; power rationing and epic blackouts are common. In a desperate move to halt environmental disaster by reducing population pressure, the Kenyan government evicted tens of thousands of people from the land.

Severe drought, temperature extremes, formerly productive land gone barren: this is climate change. Yet, says botanist Jan Pokorny of Charles University in Prague, these snippets from Kenya are not about greenhouse gases, but rather the way that land-use changes—specifically deforestation—affect climate; newly tree-free ground “represents huge amounts of solar energy changed into sensible heat, i.e. hot air.” Pokorny, who uses satellite technology to measure changes in land-surface and temperatures, has done research in western Kenya for 25 years, and watched the area grow hotter and drier. The change from forest cover to bare ground leads to more heat and drought, he says. More than half the country used to be forested; it's now less than 2 percent. 
Each year Earth loses 12 million to 15 million hectares of forest, according to the World Wildlife Fund, the equivalent of 36 football fields disappearing per minute. Although forests are ebbing throughout the world, in Africa forest-climate dynamics are easily grasped: according to the United Nations Environmental Programme, the continent is losing forests at twice the global rate. Says Pokorny, the conversion of forest to agricultural land, a change that took centuries in Europe, “happened during one generation in western Kenya.” Pokorny's work, coupled with a controversial new theory called the “biotic pump,” suggests that transforming landscapes from forest to field has at least as big an impact on regional climate as greenhouse gas–induced global warming.
Scientific American: Melting Arctic Ice Will Make Way for More Ships--and More Species Invasions
A new study shows immense increases in shipping are likely over the North Pole and Arctic Ocean in the coming years, alerting scientists who study invasive species
By Lisa Palmer
March 6, 2013
The rare ships that have ventured through the harsh, icebound Arctic Ocean require reinforced hulls and ice-breaking bows that allow them to plow through dense ice as much as two meters deep, and face hazardous conditions in remote locations for long periods of time. Arctic sea ice now is melting so rapidly each summer due to global warming, however, that ships without ice-breaking hulls will be able to cross previously inaccessible parts of the Arctic Ocean by 2050. And light-weight ships equipped to cut through one meter of ice will be able to travel over the North Pole regularly in late summer, according to a new study published March 4 in Proceedings of the National Academy of Sciences Plus.

That’s good news for economic development because it offers many new and faster routes from east to west, shaving 40 percent off transportation time and fuel costs compared with shipments via the Suez Canal. But the geographic extent of trade routes across the Arctic is worrisome for scientists who study invasive species.

Ships traveling regularly in the Northwest Passage, beyond the Northern Sea Route and through the central Arctic Ocean, will likely bring new invaders to the Arctic as well as to northern ports. Mosquitoes and forest beetles are expected to survive hidden in cargo, for example. Hearty marine organisms, such as mussels and barnacles, will likely tag along as larvae in ballast tanks or in niche areas on vessel hulls. When new species flourish in a new environment they can become harmful, damaging local ecosystems and threatening native plants and animals, much as the Japanese vine known as kudzu has overrun the southern U.S. Economic costs associated with new pests have been significant—for example, the influx of zebra mussels into the Great Lakes has been estimated at $1 billion annually.
Climate Wire via Scientific American: Scientists Detail Severe Future Impacts of Climate Change
At a U.S. Senate hearing, scientists warned that New Orleans, Florida and other places will be radically transformed if global warming is allowed to continue unabated
By Tiffany Stecker and ClimateWire
February 14, 2013
In a probable scenario for climate change, New Orleans will no longer exist. Neither will Atlantic City, N.J. Boston will look much like it did in the 17th century, before the city was dredged up to build a port. And Florida will no longer keep its distinct appendage shape.

These geographical changes due to sea-level rise are only the beginning, scientists bluntly stated at a briefing yesterday convened by Senate Environment and Public Works Committee Chairwoman Barbara Boxer (D-Calif.). 
"Today's talk underscored what I already knew, but gives me more facts," said Boxer. "We have to act because our children and our grandchildren need us to act."
Reuters via Scientific American: Drought Joins U.S. Farmers in the Field for Spring Planting
By Charles Abbott
February 15, 2013
WASHINGTON (Reuters) - U.S. farmers will plant crops this spring under the shadow of a persistent drought that grips prime farmland from the Mississippi River to the Rocky Mountains, with grain supplies already tight from drought losses in 2012.

In all, 56 percent of the contiguous United States is under moderate to exceptional drought, twice the usual amount, the Senate Agriculture Committee was told on Thursday.

Arid weather was expected to run until May in the wheat-growing Plains and in the western Corn Belt, where corn and soybeans are the major crops.
Science News: Warmer is not always wetter
Compared to global warming caused by solar radiation, global warming caused by greenhouse gases results in less rainfall, simulations suggest
By Erin Wayman
Web edition: January 30, 2013
Not all warming is the same. For the same increase in temperature, global warming caused by greenhouse gases results in less rainfall than does warming caused by the sun’s radiation, climate simulations suggest.

Because wet places should get more rain as the climate heats up, the new results may explain the mystery of why a warm period 1,000 years ago was wetter than the warm late 20th century. Jian Liu of the Chinese Academy of Sciences in Nanjing and colleagues describe these results in the Jan. 31 Nature.

“If what they show holds up, it’s good news in that it helps reconcile an apparent contradiction,” says oceanographer Gabriel Vecchi of the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton, N.J. But it would also limit how scientists can use some past episodes of climate change as analogs for the future, he says.

No comments:

Post a Comment