We have all heard about the Ice Age, if only in cartoon movies. A time when massive ice sheets covered the planet while mammoths and saber toothed cats roamed the frozen landscape. What is more, the cycle of interglacial-glacial-interglacial has happened over and over again during the past million or so years. During the last half a million years the cycle has repeated every 130,000 years, with the warm period we are now enjoying—the Holocene—just the latest interglacial respite from the icy conditions of the Pleistocene Ice Age. What most people don't know is that there were many areas on Earth that remained unchanged, even during the height of the last glacial period. The Sahara was hot and dry, and in the Amazon rainforests, though a bit smaller in area, looked much like they do today.
One of the scary scenarios frequently trotted out by climate change alarmists is the possible shutdown of the ocean currents in the Atlantic Ocean. This would disrupt northern hemisphere climate, particularly in Europe. Indeed, one Hollywood disaster movie had frozen military helicopters falling from the skies in the UK and Manhattan buried under a tsunami of ice. We are told this could happen at any time, if the world gets too hot from all that CO2 our species is churning out. Now a shocking new paper in the journal Science implies that the standard view of a relatively stable interglacial circulation may not hold for conditions warmer/fresher than at present. Why? Because it happened before, over 100,000 years ago, without the help of man made global warming. Another catastrophic climate threat is shown to be totally natural and to have happened before our species began burning coal and driving SUVs.
A study of ancient volcanic ash found at key archaeological sites across Europe suggests that early modern humans were more resilient to climate change and natural disasters than commonly thought. The study, which appeared in PNAS, analyzed volcanic ash from a major eruption that occurred in Europe around 40,000 years ago. The volcano spewed so much ash that the event probably created winter-like conditions and a sudden colder shift in climate. Scientists have generally suggested that the spread of modern humans, and the decline of our cousins the Neanderthals, was primarily due to ancient volcanic eruptions and deteriorating climate conditions, but this study shows that stone-age man rolled with the punches and shrugged off the sudden shifts in climate. This new evidence flies in the face of modern predictions that a shift of a few degrees in average yearly temperature will decimate human populations world wide.
Between 15 and 20 million years (Myr) ago, Earth's climate took a pause during its long slide into the Pleistocene Ice Age for a period of real global warming. During this relatively brief time glaciers around the world retreated and there are indications that, at least around the edges of the continent, there was significant vegetation on Antarctica. Temperatures may have been as high as 11°C higher than today. Scientists say this global warm spell took place under under CO2 levels in the range of 190–850 ppmv, both significantly higher and lower than today's 390 ppmv. It is hoped that studying conditions during the Miocene warming can provide constraints on the fundamental laws governing the climate system. Why? If the Pleistocene Ice Age is truly coming to an end, as some have said, this may be the climate of the future.
Around 19,000 years ago, oceanic conditions underwent dramatic changes that coincided with a shift in global climate, marking the onset of the Holocene warming. In the North Atlantic, major changes in the Meridional Overturning Circulation (MOC), which carries warm and highly saline surface water north to cooler regions, played a substantial role in regulating climate and levels of atmospheric carbon dioxide. Scientists are now convinced that the ocean absorbed, stored, and released vast quantities of carbon in the past, playing a major role in the end of the last Pleistocene Ice Age glacial period. Understanding the ocean's role in the past is important to understanding how it may influence climate in the future. A new report in Science shows that the MOC experienced a series of abrupt changes that lasted from decades to centuries, and may have stored and released more CO2 than previously thought.
Scientists believe that carbon released from the ocean floor played a key role in past episodes of climate change. Around 55 million years ago, the break-up of the northeast Atlantic continents was associated with the injection of large amounts of molten magma into seafloor sediments. Formation of the North Atlantic basalts heated the carbon-rich sediments, triggering the release of large quantities of methane and carbon dioxide into the ocean and atmosphere. It has been suggested that this release of previously sequestered carbon was responsible for a 100,000 year period of rapid temperature rise known as the Paleocene-Eocene Thermal Maximum or PETM. Three letters published in Nature Geoscience suggest that carbon trapped beneath the seabed continues to influence carbon dynamics, at least in the deep ocean.
To ring in the new year, The Resilient Earth presents a collection of recent journal and news articles regarding climate science. Some are about actual science and others are more in the way of commentary on the state of global warming. New discoveries continue to be made, though the climate change faithful stubbornly refuse to abandon the party line: Earth's temperature is going to rise dangerously and humanity is to blame. Perhaps the most interesting development is that a number of green advocates have given up on avoiding global warming, deciding instead to stress the unfair social impacts that climate change will supposedly cause. At the end of 2010, here is a snapshot of the state of the climate change debate.
Like an overly familiar maniac from a series of Hollywood slasher movies, CO2 has lost most of its ability to scare the public. Carbon dioxide's diminishing fright mojo has sent climate change alarmists—and those in the media who lend them mindless support in trade for salacious headlines—casting about for a next gas molecule to scare the public with. A few trial balloons have been floated for oxides of nitrogen (NOx) but the rising star in the global warming shop of horrors is methane (CH4). Aside from having a familial relation ship with CO2 based on carbon, CH4 is a known greenhouse gas and is produced almost everywhere on Earth by decaying organic matter. Most recently, there were panicked warnings that Arctic seabed methane stores were being destabilized. The hype over methane has gotten so out of hand that a news focus article in Science (which is not a hot bed of climate change skepticism) has publicly stated the situation is being exaggerated.
According to a recent paper, human actions may have caused Earth's climate to warm much earlier than previously expected. In an article to be published in Geophysical Research Letters, and widely reported in the media, around 15,000 years ago, early hunters were a major factor in driving mammoths to extinction. Supposedly, this die-off had the side effect of heating up the planet. This is an interesting conjecture, since a letter just published in Nature Geocience reaches the opposite conclusion regarding climate and the mammoths' decline. This mammoth confusion illustrates the uncertain and even contradictory evidence that abounds in climate science.
Earth's climate history includes numerous incidents of rapid warming and cooling. While Pleistocene ice-age glacial terminations are arguably the most dramatic recent examples of sudden climate change, during the last glacial period the climate of the Northern Hemisphere experienced several other significant episodes when the climate rapidly warmed. Scientists call these episodes Dansgaard-Oeschger (DO) events after the Danish and Swiss researchers who documented them using ice-core studies. These rapid oscillations are marked by rapid warming, followed by slower cooling. The most prominent coolings are associated with massive iceberg discharge into the North Atlantic Ocean known as Heinrich events (HE). The melting icebergs add large volumes of cold fresh water to the ocean, disrupting circulation patterns and causing further climate changes. Scientists look to past events like these to help us understand how Earth's climate system functions—what causes our planet to cool or suddenly warm. Recently, new data on past climate changes have led one commentator to predict the end of winter skiing in the American Southwest.
Twenty thousand years ago, North America had a more impressive array of big animals than Africa does today. The continent was populated by mastodon, several species of mammoth, giant ground sloths, saber-toothed cats and bison twice the size of their modern counterparts. By 10,000 years ago most of these animals were gone, including the 10 species that weighed more than a ton. Many drastic changes occurred during this interval, including the arrival of Homo sapiens to the new world. Many have cited humans as the cause of this great megafaunal die-off: were H. sapiens causing mass extinctions even during the stone age?
A new study has confirmed the astronomical theory of the ice ages, but with a new twist: The shutoff of the meridional ocean circulation, or MOC, and an associated southward shift of tropical monsoon rain belts seems to play an integral role in the melting of glacial period ice sheets. These changes cause warming of the Southern Hemisphere and a rise in atmospheric CO2 levels, which in turn provides a positive feedback loop that helps drive glacial termination. This is why, every 100,000 years or so, the great Northern Hemisphere ice sheets collapse and glacial conditions give way to a warm interglacial period, such as the Holocene warming humanity is currently enjoying. This, however, does not support recent claims that global warming is causing the Southeast Asian monsoon to fail.
Two articles in the July 17 edition of Science describe efforts to model Earth's rapidly changing climate at the end of the last glacial period, between 21 and 11 thousand years years ago (ka). After a year and a half of number crunching on Oak Ridge National Laboratory's Jaguar supercomputer, the first results indicate that climate experienced cooling 17 ka, during the Heinrich Event 1 (H1), followed by an abrupt warming at the onset of the Bølling-Allerød Warming 14.5 ka. These abrupt climate changes were accompanied by large changes in the “ocean conveyor belt”: the Atlantic meridional overturning circulation (AMOC). The results suggest that this transition can be viewed simply as the North Atlantic climate response to rapidly changing glacial meltwater flow. The findings call for a paradigm shift in our understanding of abrupt climate change and weakens the threat of “irreversible tipping points” so popular with climate change extremists.
The current hot phrase bandied about by talking heads and parotted by news pundits is “tipping point.” We are told that the climate may be near a tipping point, if it has not crossed one already, and that can't be good. But what is a tipping point, where do they come from and how can we identify one when we see it?
Here are some interesting climate related tidbits from the science news feeds; food for thought in the new year. First, researchers at the University of Oregon have discovered evidence linking the disappearance of North American megafauna, the Clovis people and the onset of the Younger Dryas period to a comet impact. For years scientists have blamed the disappearance of the American Mammoth, Mastodon, saber toothed cats and other large land animals on human predation or climate change.