* Astronomy

Blobrana · L

RE: Ancient climate

Blobrana · L

A new study has indicated that global warming 55 million years ago triggered a massive release of greenhouse gases into the atmosphere which led to a huge spike in temperatures.
Appy Sluijs, a paleoecologist at Utrecht University in the Netherlands, and his colleagues, carried out the study.
Evidence in support of this theory comes from the abundance and distribution of marine algae, which indicate that the environment started to change and the ocean surface began to warm several thousand years before the large temperature spike.
Scientists have long studied this ancient temperature spike, called the Palaeocene-Eocene thermal maximum (PETM), for clues to what could happen as a result of todays global warming.

Read more

Blobrana · L

New Ice Age Map Reveals Geologic Wonders of Downeast Region

My first inkling that coastal Maine was not always terra firma came with finding tiny mollusc shells in a gravel pit where I used to play, growing up near Portland.
Indeed, some 15,000 years ago the Maine coast, weighted down under the 1.5-mile-deep Laurentide Ice Sheet, was inundated by ocean waters
Read more

Blobrana · L

Researchers have long speculated that ancient climate changes have had a powerful influence on human evolution, spurring our ancestors to walk upright, to migrate out of Africa, and to adapt to varied habitats. Now, scientists have found a concrete example: evidence of intense droughts in tropical Africa right when many anatomically modern humans were probably dying. The new findings provide an ecological explanation for the Out-of-Africa hypothesis that all modern humans are descended from a small number of ancestors who survived a population bottleneck in Africa between 150,000 and 70,000 years ago and gave rise to offspring who migrated to Asia and Europe.

Source

Blobrana · L

Scientists have discovered that some deep sea sponges have growth bands that, like tree rings, can reveal past environmental conditions. The bands show that, far from being a constant environment, the deep ocean experiences changes akin to seasons.
Scientists from New Zealands National Institute of Water & Atmospheric Research (NIWA) and New Caledonias Institut de Recherche pour le Developement (IRD) found seasonal fluctuations in levels of carbon and trace metals in a lithistid (rock) sponge aged over 135 years. The research was published in the September issue of the journal Limnology & Oceanography.

Read more

Blobrana · L

When Georgia Tech Assistant Professor Kim Cobb and graduate student Jud Partin wanted to understand the mechanisms that drove the abrupt climate change events that occurred thousands of years ago, they didnt drill for ice cores from the glaciers of Greenland or the icy plains of Antarctica, as is customary for paleoclimatolgists. Instead, they went underground.
Growing inside the caves of the tropical Pacific island of Borneo are some of the keys to understanding how the Earths climate suddenly changed - several times - over the last 25,000 years. By analysing stalagmites, the pillar-like rock formations that stem from the ground in caves, they were able to produce a high-resolution and continuous record of the climate over this equatorial rainforest.

"These stalagmites are, in essence, tropical ice cores forming over thousands of years. Each layer of the rock contains important chemical traces that help us determine what was going on in the climate thousands of years ago, much like the ice cores drilled from Greenland or Antarctica - Jud Partin.

Read more

Blobrana · L

A 55 million-year-old British bog uncovered by the Channel Tunnel rail link is giving scientists insights into a ancient period of global warming.
The researchers found methane released from the bogs played a major role in the Palaeocene-Eocene thermal maximum, when temperatures suddenly rose.
They suggest in the journal Nature that this is likely to clarify the role of bogs in present-day global warming.
Methane released by warmer conditions could make temperatures rise faster.

Read more

Blobrana · L

The Eocene epoch

Blobrana · L

RE: Ancient climate

Blobrana · L

Fossilised midges have helped scientists at the University of Liverpool identify two episodes of abrupt climate change that suggest the UK climate is not as stable as previously thought.
The episodes were discovered at a study in Hawes Water in Northern Lancashire, where the team used a unique combination of isotope studies and analysis of fossilised midge heads. Together they indicated where the climate shifts occurred and the temperature of the atmosphere at the time.
The first shift detected occurred around 9,000 years ago and the second around 8,000 years ago. Evidence suggests that these shifts were due to changes in the Gulf Stream, which normally keeps the UK climate warm and wet.
During each shift the North West climate cooled with an average summer temperature fall of 1.6 degrees approximately three times the amount of temperature change currently attributed to global warming.
Scientists found that the atmosphere cooled rapidly and cold periods lasted up to 50 years for one event and 150 years for the other. The detection of these events will allow experts to understand more clearly what can happen when the climate system is disturbed.

At Hawes Water mud has been deposited continuously without any gaps, which allows us to measure an accurate timeline of events. We have monitored the modern environment of the lake for the past eight years and this has shown us how to read the past climate record from the ancient mud in the lake. Isotope analysis helped us identify the episodes of climate change. We then used fossilised heads of non-biting midges, which are preserved in every spoonful of mud. They tell us the temperature at the time the mud was deposited. We compare the population of midge heads in each sediment sample with the population of midges in Scandinavian lakes, which span a wide range of modern day temperatures - Professor Jim Marshall, from the Universitys Department of Earth and Ocean Sciences.

The team found the two abrupt climate changes correlated directly with two episodes of sharp climate deterioration in areas such as Greenland, suggesting that a change in the Gulf Stream had occurred.

People are worried that the melting of the polar ice caps could result in a slow-down of what we call the Atlantic Conveyer. This is where cold water that sinks in the far north is replaced by warmer water from the tropics in its circulation of the North Atlantic Ocean. A number of studies suggest that the conveyer may be unstable and may be able to slow down or switch off completely, making our climate suddenly colder. Our study provides evidence that the two climate shifts we detected were directly linked to a slow-down in the conveyer - Professor Jim Marshall.

Scientists believe that this new data will provided a unique test for the global climate computer models that are being used to simulate future climate change.
The research - in collaboration with University of Swansea; the Open University; University of Exeter; Edge Hill University and University College London - is published in Geology.

Source