Marine and terrestrial proxy records suggest that there was a peak in global warming between 10,000 and 6,000 years ago, following the end of the last glacial period. Since the Holocene Thermal Maximum, Earth has undergone global cooling. The physical mechanism responsible for this global cooling has remained unknown and doesn't fit in with the current CO2 based climate models. Those climate models generate a robust global annual mean warming throughout the Holocene, mainly in response to rising CO2 levels and albedo changes due to retreating of ice sheets. In other words, the models disagree with reality, and when models disagree with nature the models have a credibility gap. A new paper in the Proceedings of the National Academy of Sciences (PNAS) says this model-data inconsistency indicates a critical reexamination of both proxy data and models is called for.
One of the greatest failures of climate science has been the dismal performance of general circulation models (GCM) to accurately predict Earth's future climate. For more than three decades huge predictive models, run on the biggest supercomputers available, have labored mighty and turned out garbage. Their most obvious failure was missing the now almost eighteen year “hiatus,” the pause in temperature rise that has confounded climate alarmists and serious scientists alike. So poor has been the models' performance that some climate scientists are calling for them to be torn down and built anew, this time using different principles. They want to adopt stochastic methods—so called Monte Carlo simulations based on probabilities and randomness—in place of today’s physics based models.
Scientists have long suspected that the orbital cycles of our planet are responsible for the periodic climate variation that causes alternating glacial and interglacial periods. Milankovitch's theory of orbital cycles suggests that summer insolation at high northern latitudes drives the glacial cycles. Moreover, statistical analyses have demonstrated that the glacial cycles are indeed linked to eccentricity, obliquity and precession. Now, researchers have confirmed that a combination of two of the Milankovitch cycles conspire to start and stop ice ages. The 100,000-year eccentricity cycle amplifies the influence of the 23,000-year wobble of Earth's spin axis called precession. The new modeling also suggests that the great accumulation of mass by the North American ice sheet causes the abrupt end of glacial periods. CO2 is involved, but is not determinative, in the evolution of the 100,000-year glacial cycles say the scientists.
Most people have never heard of the Anthropocene era and with good reason—it is not an officially recognized geologic time period. It is the invention of a small group of scientific busy bodies who evidently have nothing better to do than try to effect a change in the official timeline of Earth's past. The International Commission on Stratigraphy, the body charged with formally designating geological time periods, has been petitioned in the past and just recently a group of chuckle-heads attending the Society for American Archaeology meetings in Hawaii have brought the idea up again. Only problem is, the proponents of the Anthropocene have fallen to arguing amongst themselves—when did the “Age of Man” really start?
Instrument data from the last 160 years indicate a general warming trend during that span of time. However, when this period is examined in the light of palaeoclimate reconstructions, the recent warming appears to be a part of more systematic fluctuations. Specifically, it is an expected warming period following the 200-year “Little Ice Age” cold period. Moreover, a new study of the natural variability of past climate, as seen from available proxy information, finds a synthesis between the Milankovitch cycles and Hurst–Kolmogorov (HK) stochastic dynamics—a result that shows multi-scale climate fluctuations cannot be described adequately by classical statistics.
There has been a wave of triumphal announcements by climate change proponents recently, almost giddy over the summer shrinkage of the Arctic ice sheet. “Lowest level ever!” they proclaim, thought that is not quite true. Nonetheless, The Arctic pack ice has been receding over the last decade or so, but that is only natural. You see, there is a well known, if poorly understood, linkage between the ice at the north pole and the ice in and around Antarctica—and the ice around Antarctica is doing quite well. Satellite radar altimetry measurements indicate that the East Antarctic ice sheet interior increased in mass by 45±7 billion metric tons per year from 1992 to 2003. This trend continues today, reinforcing recent scientific investigations into this millennial scale oscillation between the poles. According to studies, this is how things have been for hundreds of thousands of years.
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.
A new theory of supercontinent formation, published in the journal Nature, predicts that the Arctic ocean will be squeezed out of existence in the future as most of Earth's landmass gathers in a new supercontinent—Amasia. The new orthoversion helps to resolve the problems of the older introversion and extroversion models, which have led to a “fundamental disconnection … between the geologic evidence for supercontinent formation, and the models purported to explain their assembly.” If the Arctic Ocean disappears so will the Polar Bear, an iconic species that has been held up as a poster child for global warming. The climate catastrophists are correct in predicting the demise of the white bear of the Arctic, but they have both the reason and time frame terribly wrong.
Tracking the flow of ice in the Arctic is difficult. Reconstructing the extent and flow in times past is even more difficult. An interesting new report has turned to driftwood, embedded in the Arctic pack ice, as a way of deciphering Arctic climate conditions over the last 10,000 years. The researchers found a climate record that is in good agreement with previous histories, including such events as the Medieval Warm Period, the Little Ice Age and the Holocene Thermal Maximum. In fact, they found temperatures during the HTM to be 2° to 4°C higher than today. They also found a complementarity oscillation in sea-ice abundance between East and West that is not correctly simulated by current ice models.
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.
Much concern has been raised by climate scientists regarding ice loss from the world's two remaining continental ice sheets. Rapid loss of ice-mass from the glaciers of Greenland and Antarctica are cited as proof positive of global warming's onslaught. The latest measurements involve the use of satellite gravimetry, estimating the mass of terrain beneath by detecting slight changes in gravity as a satellite passes overhead. But gravity measurements of ice-mass loss are complicated by glacial isostatic adjustments—compensation for the rise or fall of the underlying crustal material. A new article in Nature Geoscience describes an innovative approach employed to derive ice-mass changes from GRACE data. The report suggests significantly smaller overall ice-mass losses than previous estimates.
The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) projected that global sea level will rise by up to 60 cm by 2100 due to global warming. The cause of this rise is twofold: expansion of ocean waters as they warm and additional water from glaciers melting. Despite nearly stable sea levels over the past 3,000 years, a number of low-lying and island nations have seized on the imminent flood as a reason to demand reparations from developed nations. In reality, most of the areas in the world that are suffering from inundation are threatened because of human actions, but not global warming. Damming and rerouting of rivers combined with over-pumping of ground water has led to subsidence in many areas—in other words, the seas are not rising, the land is sinking.
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.
There have been a rash of bogus reports in the news media about rapidly rising sea-levels supposedly caused by global warming. Sea-levels are notoriously hard to measure on a global basis since land also rises and sinks due to tectonic activity. With historical records mostly unreliable how can we tell if current conditions are normal for Earth 14,000 years after a deglaciation? A new report, based on calcium growths in caves on the Mediterranean island of Mallorca, says that sea levels around 81,000 years ago were higher than today. Higher sea-levels imply less glacial ice and warmer temperatures than today as well. Even more interesting is that this occurred during a warm period called marine isotope stage (MIS) 5a, which was more than 30,000 years after the Eemian interglacial ended and glaciation had resumed. This could mean that current theories about how ice age glacial periods start are wrong.