Sentences with phrase «hemisphere glaciation»

Meyers, S. R. & Hinnov, L. A. Northern Hemisphere glaciation and the evolution of Plio - Pleistocene climate noise.

The Northern Hemisphere glaciation, which began 3.2 million years ago, was driven by tectonic events, such as the closing of the Panama seaway and the uplift of the Andes, the Tibetan Plateau, and western parts of North America.

For example, closure of the Isthmus of Panama, and restriction of the Indonesian seaway, have been suggested as reasons for the onset of northern - hemisphere glaciation 3 million years ago (but that's 3 million, not 1 million).

Although some disputed that the «cooling trend» could result in «a return to another ice age» (the Times, Sept. 14, 1975), others anticipated «a full - blown 10,000 - year ice age» involving «extensive Northern Hemisphere glaciation» (Science News, March 1, 1975, and Science magazine, Dec. 10, 1976, respectively).

Although there is limited evidence of ice - rafted debris in the Arctic from the Miocene and into the Eocene, suggesting some continental glaciation (Stickley et al., 2009; St. John and Krissek, 2002), empirical evidence suggests that widespread Northern Hemisphere glaciation did not occur until 2.75 Ma (Ravelo et al., 2004), which is substantiated by recent Pliocene paleotemperature SST estimates near Svalbard between 10 and 18 °C (Robinson, 2009).

It has also been proposed that the termination of a permanent El Niño - like state may have been a positive forcing mechanism for the intensification of Northern Hemisphere glaciation ca 2.7 Ma BP (Cane & Molnar 2001; Philander & Fedorov 2003; Huybers & Molnar 2007).

Since the onset of the Northern Hemisphere glaciation (~ 2.7 million years ago), Earth's climate has undergone large transitions between cold «glacial» and warm «interglacial» (e.g., present - day) stages.

It's not confirmed, but is believed that this established the Gulf Stream leading to the Northern Hemisphere glaciation (NHG), the build - up of the Laurentide and Scandinavian ice - sheets.

C: Datasets suggesting a drying environment at 2.5 Ma, shown by λ 18O from benthic foraminifera, a proxy for global temperature, smoothed with a Gaussian window of 200 ky; eustatic sea level; and magnetic susceptibility, a proxy for ice rafted debris and Northern Hemisphere glaciation.

The second clue is that Northern Hemisphere glaciation intensified between 3.1 and 2.5 million years ago, thanks to all the moisture delivered to the far north via evaporation from a more vigorous Gulf Stream.

Finally, Callendar 1938 closed with the relatively optimistic comment that, in addition to the direct benefits of heat and power, there would be indirect benefits at the northern margin of cultivation, through carbon dioxide fertilization of plant growth and even delay the return of Northern Hemisphere glaciation:

A model (based on orbit) predicts Northern Hemisphere glaciation.»

The paper was motivated by the idea that the timing of Antarctic glacial movements was set by sea - level changes that reflected Northern Hemisphere glaciation.

Here we propose that increasing variablility within the past million yearsmay indicate that the climate system was approaching a second climate bifurcation point, after which it would transition again to a new stable state characterized by permanent mid-latitude Northern Hemisphere glaciation.

Science magazine (Dec. 10, 1976) warned of «extensive Northern Hemisphere glaciation.»

For example, closure of the Isthmus of Panama, and restriction of the Indonesian seaway, have been suggested as reasons for the onset of northern - hemisphere glaciation 3 million years ago (but that's 3 million, not 1 million).

From the onset of northern - hemisphere glaciation (about 3 million years ago) to the «mid-Pleistocene transition» (about 800,000 years ago), glacial advance and retreat follows a strong 41,000 - year cycle, which has led to its being called «the 41 ky world» (Raymo & Nisancioglu 2003, Paleoceanography, 18, 1011).

Beyond the onset of northern hemisphere glaciations, some ~ 2.8 Mya, which is some 2 or so million years older than we can really guess which came first, it becomes sort of a «silly - buggers» game.

Subsequently, large Northern Hemisphere glaciations began to occur when pCO2 dropped below about 300 ppm in the middle Pliocene.

Not exact matches

If he's worried about ice ages, perhaps he should ponder the selfishness of squandering what could have been a useful geoengineering resource to future generations faced with an imminent glaciation; carefully burning fossil fuels to enhance the greenhouse effect just enough to maintain temperatures in the face of declining northern - hemisphere insolation due to the Milankovich cycles may well be the most cost - effective method for them to do so, if those resources are still around at the time.

-- these aren't contradictory results, they're (from different hemispheres, from different glaciations, from different species, from different ice cores, from....

Do you think you can convince me that we aren't in a interglacial period that is getting a bit long in tooth, that the Milankovitch cycle that helps the glaciers grow by making northern hemisphere winters warmer and summers cooler isn't moving in the direction favorable to glaciation, and that the next once - per - thousand year volcanic eruption won't happen in this century, and it won't be the straw that breaks the camel's back by lowering the earth's temperature a couple degrees for a few years to mark the end of the Holocene?

If these plumes of warm air operated in the same way during the last glaciation as they do know then they would make short work of ice sheets that were hanging around because of the albedo effect, this is possible because not all the northern hemisphere mid latitude land surface was covered with ice throughout the period of glaciation and might explain why glaciations terminate quickly

The Cenozoic record also reveals the amplification of climate change that occurs with growth or decay of ice sheets, as is apparent at about 34 Myr BP when the Earth became cool enough for large - scale glaciation of Antarctica and in the most recent 3 — 5 Myr with the growth of Northern Hemisphere ice sheets.

Interglacials, they say, can be predicted by just two factors: the amount of sunlight that hits the Northern Hemisphere during the summer and the length of the glaciation that preceded it.

The predominance of landmasses in the northern hemisphere causes glaciations to predominate over interglacials by about 9 to 1 with a full cycle every 100, 000 years helped along by the orbital changes of the Milankovitch cycles that affect the pattern of insolation on those shifting cloud masses.

Then in his Figure 1 Hansen shows Antarctic glaciation when deep ocean temperature was approx 3deg C and later the N. hemisphere ice sheet forming at say 2.5 deg C deep ocean temperature.

This is corroborated by model simulations indicating that atmospheric CO2 levels must fall below 280 ppmv to promote widespread continental glaciation of the Northern Hemisphere (DeConto et al., 2008) and 250 ppmv to promote major continental glaciation on Greenland (Lunt et al., 2008), both of which are well below recent estimates of Pliocene atmospheric CO2 estimates of ∼ 390 ppmv (Pagani et al., 2010).