Sentences with phrase «recent glaciation»

They have not had the remaking influences of fairly recent glaciation and sedimentation, followed by the biological colonization typical of many rich lands in more temperate zones.

Not exact matches

It is also the longest period of globally stable climate and sea level in at least the last 400,000 most recent years of seesaw between glaciation and warmer times.

So, Retallack suggests, colonization of the land by vascular and nonvascular plants together may help explain the massive drawdown of CO2 that triggered the most recent and stronger of the two major glaciations that Lenton and his colleagues studied.

During the most recent North American glaciation, during the latter part of the Wisconsin Stage (26,000 to 13,300 years ago), ice sheets extended to about 45 degrees north latitude.

For a while, it was thought that the glaciation of Antarctica may have significantly contributed to the cooling of the ocean, however, recent evidence tends to deny this.

In the preface to his book on «Climatic History and the Future» H.H. Lamb says: «Recent research...... has rendered more specific the expectation that the beginnings of the next glaciation will be upon our descendants within 3000 to 7000 years.

The most recent period of glaciation, which many people think of as the «Ice Age,» was at its height approximately 20,000 years ago.

The conclusion that timely anthropogenic CO2 emissions have rescued the biosphere from a long term glacial slide down to dangerously low photosynthesis - stopping CO2 levels (that were approached during the recent Wisconsin glaciation) is based on multiple independent lines of evidence and the vast body of peer - reviewed science.

The most recent major glaciation occurred during the late Ordovician, 440 million years ago, when atmospheric CO2 was estimated to be above 5,000 ppmv.

Much of Miller's work has been the articulation of Late Holocene glaciation, up to and including its relative maximum in the Little Ice Age, from which numerous Baffin Island locations are still emerging in his recent study.

Given that a CO2 doubling or halving is equivalent to a 2 % change in solar irradiance [66] and the estimate that solar irradiance was approximately 6 % lower 600 Ma at the most recent snowball Earth occurrence [113], figure 7 implies that about 300 ppm CO2 or less was sufficiently small to initiate glaciation at that time.

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.

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).

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).

As recently as 18,000 years ago, at the height of the most recent major glaciation, CO2 dipped to its lowest level in recorded history at 180 ppm, low enough to stunt plant growth.

The most recent period of cooling and glaciation began approximately 120,000 years ago.