Beautiful Wind Map

There's a beautiful moving map of the wind for the United States at http://hint.fm/wind/. This is the moving wind map during Hurricane Sandy on October 30, 2012.

Younger Dryas Impact?

The Younger Dryas was a cold period about 12,000 years ago that lasted about a thousand years. The previous ice age had seemingly ended, but then the Younger Dryas was a return to cold conditions. Many large animals became extinct around that time, possibly because of the rapidly changing climate.
There is a controversial hypothesis that the Younger Dryas was caused by an extraterrestrial impact. See Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling for the original article in PNAS (2007). The controversy peaked with this highly skeptical article Mammoth-Killer Impact Flunks Out in Science (2010).

After a new study failed to find nanodiamonds, impact experts are flatly rejecting outsiders' claims that an impact 12,900 years ago devastated the megafauna.

However the proponents of the impact hypothesis have not surrendered! Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis in PNAS (2012) details new evidence from lake sediments in Mexico.

The Mid-Pleistocene Transition

Before 1.2 million years ago, glacial cycles had a 40,000 year periodicity. But in the past 700,000 years the ice-age cycle has been around 100,000 years. There was a transitional period in between. See Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition from 2009 in Science magazine. There is a 41,000 year periodicity in the earth's orbit which could explain the earlier periodicity (see Milankovitch cycles), but the the transition to the more recent 100,000 year cycle is currently rather mysterious.

An Unusual Earlier Ice Age

There was an earlier ice age in the southern supercontinent Gondwana at the boundary between the Ordovician and Silurian periods around 445 million years ago. This ice age was unusual in that it occurred while CO2 levels were high and also coincided with a major extinction event. See The Magnitude and Duration of Late Ordovician–Early Silurian Glaciation in Science.

Human Activity and Fires

Humans cause fires, right? Only You Can Prevent Forest Fires! It might seem that in places and times with less human presence and activity there should be fewer fires. But there is now evidence to the contrary: The Burning Issue in Science reports that evidence from Antarctic ice cores shows declining levels of fire in the Southern Hemisphere until the 1600's, followed by a dramatic peak in the 1800's and now unprecedented low levels of burning.

Atlantic Deep Water Reversal

Warm water sinks in the North Atlantic, forming a deep water current which flows southward at the bottom of the Atlantic all the way to Antarctica.  This has a profound effect on our climate - for example, contributing to the warm temperatures Europe enjoys despite its northernly latitude.  However, during the last Ice Age the deep Atlantic current may have actually been reversed, flowing instead from south to north.  See Reversed flow of Atlantic deep water during the Last Glacial Maximum in Nature.

North Pacific Deep Water Formation in the last ice age

When Still Waters Ran Deep in Science.

"Deep water" and "bottom water"—the waters that fill the deep parts of ocean basins—form when surface waters become dense and sink. Today, this occurs in the northern North Atlantic and around Antarctica, but not in the North Pacific. There, surface waters do not become dense enough to sink more than a few hundred meters. In the past, however, it seems things were different. Recently, Okazaki et al. offered new insight into the ancient history of the ocean from radiocarbon data and modeling analyses (1). They suggest that deep water formed in the North Pacific at the beginning of the transition out of the last ice age.

Ice Age Terminations

The Last Glacial Termination in Science.

A major puzzle of paleoclimatology is why, after a long interval of cooling climate, each late Quaternary ice age ended with a relatively short warming leg called a termination. We here offer a comprehensive hypothesis of how Earth emerged from the last global ice age. A prerequisite was the growth of very large Northern Hemisphere ice sheets, whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation. The Southern Hemisphere westerlies shifted poleward during each northern stadial, producing pulses of ocean upwelling and warming that together accounted for much of the termination in the Southern Ocean and Antarctica. Rising atmospheric CO2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres.

Freshwater Outburst from Lake Superior as a Trigger for the Cold Event 9300 Years Ago in Science.

Paleoclimate proxy records reveal a pervasive cooling event with a Northern Hemispheric extent ~9300 years ago. Coeval changes in the oceanic circulation of the North Atlantic imply freshwater forcing. However, the source, magnitude, and routing of meltwater have remained unknown. Located in central North America, Lake Superior is a key site for regulating the outflow of glacial meltwater to the oceans. Here, we show evidence for an ~45-meter rapid lake-level fall in this basin, centered on 9300 calibrated years before the present, due to the failure of a glacial drift dam on the southeast corner of the lake. We ascribe the widespread climate anomaly ~9300 years ago to this freshwater outburst delivered to the North Atlantic Ocean through the Lake Huron–North Bay–Ottawa River–St. Lawrence River valleys

Paleocene-Eocene Thermal Maximum

Did Monster Eruptions Warm the World? in Science.
The Paleocene-Eocene Thermal Maximum occured 55 million years ago. Temperatures rose over 5C and there were mass extinctions - many classes of current mammals arose afterwards. Researchers have recently found evidence of massive undersea volcanic eruptions near Iceland from that time period. The volcanic release of methane may have caused the warming.

Why was the ancient Earth so warm?

Early Earth: Faint young Sun redux Early in the Earth's history (several billion years ago) it is thought that the Sun was dimmer, so much so that the oceans would have been frozen. However there is ample evidence that the oceans were mostly liquid during that period. Greenhouse gases in the atmosphere may have kept the Earth warm. But there's a new theory that the Earth's surface may have also been darker in the past, allowing it to retain more heat from the fainter sun and resulting in warmer temperatures.

Ice Age Flood went to the Arctic not Atlantic

River reveals chilling tracks of ancient flood in Nature. After the end of the last ice age there was another cool period, the Younger Dryas, 13,000 years ago. One theory was that a huge freshwater lake in Canada, formed from melted glaciers, suddenly drained into the North Atlantic, disrupted the warm water conveyer belt there, resulting in a resumption of cold conditions in the Northern Hemisphere. But now it appears that instead Lake Agassiz drained north into the Arctic Ocean. Did that flood still cause the Younger Dryas cold period?

Cosmic Impact at the Younger Dryas Boundary

Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments

The long-standing controversy regarding the late Pleistocene megafaunal extinctions in North America has been invigorated by a hypothesis implicating a cosmic impact at the Ållerød-Younger Dryas boundary or YDB (≈12,900 ± 100 cal BP or 10,900 ± 100 14C years). Abrupt ecosystem disruption caused by this event may have triggered the megafaunal extinctions, along with reductions in other animal populations, including humans. The hypothesis remains controversial due to absence of shocked minerals, tektites, and impact craters. Here, we report the presence of shock-synthesized hexagonal nanodiamonds (lonsdaleite) in YDB sediments dating to ≈12,950 ± 50 cal BP at Arlington Canyon, Santa Rosa Island, California. Lonsdaleite is known on Earth only in meteorites and impact craters, and its presence strongly supports a cosmic impact event ...

Climate Flip-Flops

What Drives Climate Flip-Flops?

Around 14,600 years ago, the atmospheric circulation over the North Atlantic region flipped within just a few years to another state (2); also, Greenland temperatures skyrocketed by >10°C over several decades (3), terminating a cold phase known as Heinrich Event 1. The global impacts of this Bølling-Allerød transition have been well documented with climate proxy records such as sediment cores and ice cores, but the physical conditions that triggered the transition remain controversial. The temperature evolution from the Heinrich Event 1 to the Bølling-Allerød and the subsequent Younger Dryas cold phase (see the figure) is strikingly similar to the Dansgaard-Oeschger cycles (4) that dominated Northern Hemispheric climate between 60,000 and 30,000 years ago (5). Hence, unraveling the processes that triggered the Bølling-Allerød transition may also help to elucidate the mysterious, tantalizingly regular Dansgaard-Oeschger cycles (6).

Mysterious Ancient Global Warming

Ancient Climate-Change Event Puzzles Scientists

Over the past couple of decades, researchers have been gathering data about a mysterious event known as the Paleocene-Eocene Thermal Maximum (PETM). The data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 9°C within 10,000 years during the PETM, which itself started out warmer than our current world. Temperatures stayed at this elevated level for nearly 100,000 years.

A Brief History of Planet Earth

The Earth – For Physicists is an article by John Baez with a somewhat unfortunate title. You don't actually need a background in physics to follow this synopsis of the origin and development of our planet.

Hurricane Prediction

There appears to be a connection between Central Pacific Warming events and the severity and pattern of hurricanes in the North Atlantic. Central Pacific Warming events occur around the international dateline and are apparently distinct from Eastern Pacific Warming events - El Nino: Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones and Predicting El Niño's Impacts.

Sahara Dust and Atlantic Ocean Temperatures

The Role of Aerosols in the Evolution of Tropical North Atlantic Ocean Temperature Anomalies

Observations and models show that northern tropical Atlantic surface temperatures are sensitive to regional changes in stratospheric volcanic and tropospheric mineral aerosols. However, it is unknown whether the temporal variability of these aerosols is a key factor in the evolution of ocean temperature anomalies. We used a simple physical model, incorporating 26 years of satellite data, to estimate the temperature response of the ocean mixed layer to changes in aerosol loadings. Our results suggest that the mixed layer’s response to regional variability in aerosols accounts for 69% of the recent upward trend, and 67% of the detrended and 5-year low pass–filtered variance, in northern tropical Atlantic Ocean temperatures.

The Global Oceanic Conveyer Belt

There's a nice simplifed explanation of global thermohaline ocean circulation at Oceanic Conveyer Belt. The rest of the site nicely explains other aspects of "ocean motion".

Pliocene Warm Period

Greatly Expanded Tropical Warm Pool and Weakened Hadley Circulation in the Early Pliocene in Science.

The Pliocene warm interval has been difficult to explain. We reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago, during the early Pliocene. Our reconstruction shows that the meridional temperature gradient between the equator and subtropics was greatly reduced, implying a vast poleward expansion of the ocean tropical warm pool. Corroborating evidence indicates that the Pacific temperature contrast between the equator and 32°N has evolved from 2°C 4 million years ago to 8°C today. The meridional warm pool expansion evidently had enormous impacts on the Pliocene climate, including a slowdown of the atmospheric Hadley circulation and El Niño–like conditions in the equatorial region. Ultimately, sustaining a climate state with weak tropical sea surface temperature gradients may require additional mechanisms of ocean heat uptake (such as enhanced ocean vertical mixing).