An analysis of temperature data since 1500 all but rules out the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate, according to a new study by McGill Univ. physics professor Shaun Lovejoy.
The study, published in Climate Dynamics, represents a new approach to the question of whether global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels. Rather than using complex computer models to estimate the effects of greenhouse-gas emissions, Lovejoy examines historical data to assess the competing hypothesis: that warming over the past century is due to natural long-term variations in temperature.
Concerns about climate change and its impact on the world around us are growing daily. New scientific studies from the Natural History Museum of Los Angeles County working at the La Brea Tar Pits are probing the link between climate warming and the evolution of Ice Age predators, attempting to predict how animals will respond to climate change today. The La Brea Tar Pits are famous for the amazing array of Ice Age fossils found there, such as ground sloths, mammoths and predators like saber-toothed cats and powerful dire wolves. But the climate during the end of the Ice Age (50,000-11,000 years ago) was unstable, with rapid warming and cooling. The research has documented the impact of this climate change on La Brea predators for the first time.
Climate Change Slowdown Linked to Sea Surface Temp
The recent slowdown in the warming rate of the Northern Hemisphere may be a result of internal variability of the Atlantic Multidecadal Oscillation — a natural phenomenon related to sea surface temperatures, according to Penn State researchers.
"Some researchers have in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO," says Michael Mann, Distinguished Professor of Meteorology. "The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily."
Sandy Soil Deforestation is Greater Climate Threat
Deforestation may have far greater consequences for climate change in some soils than in others, according to new research led by Yale Univ. scientists. This find could provide critical insights into which ecosystems must be managed with extra care because they are vulnerable to biodiversity loss and which ecosystems are more resilient to widespread tree removal.
In a comprehensive analysis of soil collected from 11 distinct U.S. regions, from Hawaii to northern Alaska, researchers found that the extent to which deforestation disturbs underground microbial communities that regulate the loss of carbon into the atmosphere depends almost exclusively on the texture of the soil. The results were published in the journal Global Change Biology.
The Arctic has been undergoing significant changes in recent years. Average temperatures are rising twice as fast as they are elsewhere in the world. The extent and thickness of sea ice is rapidly declining. Such changes may have an impact on atmospheric conditions outside the region. Several hypotheses for how Arctic warming may be influencing mid-latitude weather patterns have been proposed recently. For example, Arctic warming could lead to a weakened jet stream resulting in more persistent weather patterns in the mid-latitudes. Or Arctic sea ice loss could lead to an increase of snow on high-latitude land, which in turn impacts the jet stream resulting in cold Eurasian and North American winters. These and other potential connections between a warming Arctic and mid-latitude weather are the subject of active research.
If the world doesn’t cut pollution of heat-trapping gases, the already noticeable harms of global warming could spiral “out of control,” the head of a United Nations scientific panel warned Monday.
And he’s not alone. The Obama White House says it is taking this new report as a call for action, with Secretary of State John Kerry saying “the costs of inaction are catastrophic.”
Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change that issued the 32-volume, 2,610-page report early Monday, told The Associated Press, “It is a call for action.” Without reductions in emissions, he said, impacts from warming “could get out of control.”
An international team of scientists has discovered that the last remaining stable portion of the Greenland ice sheet is stable no more. The finding, which will likely boost estimates of expected global sea level rise in the future, appears in Nature Climate Change.
The new result focuses on ice loss due to a major retreat of an outlet glacier connected to a long “river” of ice — known as an ice stream — that drains ice from the interior of the ice sheet. The Zachariae ice stream retreated about 20 kilometers (12.4 miles) over the last decade, the researchers conclude. For comparison, one of the fastest moving glaciers, the Jakobshavn ice stream in southwest Greenland, has retreated 35 kilometers (21.7 miles) over the last 150 years.
The jet stream is the primary driver for most weather patterns and this winter its departure from the normal lateral (west to east) movement and variations seen over the past few decades appears to have effected longer lasting stable flows with stronger and deeper north to south changes. The jet stream’s northerly flows along the U.S. Pacific coast have resulted in less rainfall in California and a significantly warmer southern Alaska region. As the jet stream reversed its flow over central northern Canada, it brought with it the Polar Vortex, resulting in long-lasting cold spells into the deep south and then strong winter storms along the eastern seaboard as it reversed once again.
Researchers studying the rings of ancient trees in mountainous central Mongolia think they may have gotten at the mystery of how small bands of nomadic Mongol horsemen united to conquer much of the world within a span of decades, 800 years ago. The rise of the great leader Genghis Khan and the start of the largest contiguous empire in human history was propelled by a temporary run of nice weather.
The rings show that exactly when the empire rose, the normally cold, arid steppes of central Asia saw their mildest, wettest weather in more than 1,000 years. Grass production must have boomed, as did vast numbers of war horses and other livestock that gave the Mongols their power. But the tree rings, spanning 1,112 years from 900 to 2011, also exhibit an ominous modern trend. Since the mid-20th century, the region has warmed rapidly, and the rings show that recent drought years were the most extreme in the record — possibly a side effect of global warming. In a region already pressed for water, the droughts have already helped spark a new migration in a vast region where people until now have lived the same way for centuries, moving herds from place to place and living in tents.
Federal forecasters predict a warming of the central Pacific Ocean this year that will change weather worldwide. And that’s good news for a weather-weary U.S.
The warming, called an El Nino, is expected to lead to fewer Atlantic hurricanes and more rain next winter for drought-stricken California and southern states, and even a milder winter for the nation’s frigid northern tier next year, meteorologists say.
Climate Change is Trapping Warm Water in Deep Ocean
In the mid-1970s, the first available satellite images of Antarctica during the polar winter revealed a huge ice-free region within the ice pack of the Weddell Sea. This ice-free region, or polynya, stayed open for three full winters before it closed.
Subsequent research showed that the opening was maintained as relatively warm waters churned upward from kilometers below the ocean’s surface and released heat from the ocean’s deepest reaches. But the polynya — which was the size of New Zealand — has not reappeared in the nearly 40 years since it closed, and scientists have since come to view it as a naturally rare event.
Climate Change Linked to Decline of Bronze Age ‘Megacities’
Scientists from the Univ. of Cambridge have demonstrated that an abrupt weakening of the summer monsoon affected northwest India 4,100 years ago. The resulting drought coincided with the beginning of the decline of the metropolis-building Indus Civilization, which spanned present-day Pakistan and India, suggesting that climate change could be why many of the major cities of the civilization were abandoned.
The research, reported in the journal Geology, involved the collection of snail shells preserved in the sediments of an ancient lake bed. By analyzing the oxygen isotopes in the shells, the scientists were able to tell how much rain fell in the lake where the snails lived thousands of years ago.