Sentences with phrase «of past ice ages»

For example, how are the causes of past ice ages relevant to that question?

Visible from space, the hole is a relic of past ice ages and was made famous by the oceanographer Jacques - Yves Cousteau.

Not exact matches

They note past ages that have been equally warm or warmer without human influence, to say nothing of repeating patterns of climate change like ice ages (though I've met one of James Hansen's computer modelers who told me with sincere conviction that there would not be another ice age).

The real purpose of myth (e.g. the creation stories) is not to give an account of what actually happened in the past, or what may happen in the future (e.g. another ice age), but to convey a particular understanding of human life.

Curiously, the decline in atmospheric oxygen over the past 800,000 years was not accompanied by any significant increase in the average amount of carbon dioxide in the atmosphere, though carbon dioxide concentrations do vary over individual ice age cycles.

Over the past 40 years, radar imagery has revealed around 150 freshwater lakes of various sizes and ages beneath the massive Antarctic ice sheet.

The observed activity of 288P also reveals information about its past, notes Agarwal: «Surface ice can not survive in the asteroid belt for the age of the Solar System but can be protected for billions of years by a refractory dust mantle, only a few metres thick.»

The discovery of ice ages in the distant past proved that climate could change radically over the entire globe, which seemed vastly beyond anything mere humans could provoke.

In fact, for temperature the major step toward the ice ages that have characterised the past two to three million years was a cooling event at 2.7 million years ago, but for ice - volume the crucial step was the development of the first intense ice age at around 2.15 million years ago.

Earth is thought to have shifted in and out of ice ages every 100,000 years or so during the past 800,000 years, but there is evidence that such a shift took place every 40,000 years prior to that time.

It provides new insight into the climatic relationships that caused the development of major ice - age cycles during the past two million years.

The overall retreat of several kilometers that has occurred over the past 20,000 years was interrupted by a stillstand or a re-advance of several hundred years at the beginning of the ACR, and then by increasingly minor glacial episodes at the end of the YD, at the beginning of the Holocene (around 10,000 years ago) and during the Little Ice Age (13th to 19th centuries).

We present a synthesis of decadally resolved proxy temperature records from poleward of 60 ° N covering the past 2000 years, which indicates that a pervasive cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age.

On land, the capacity of animals to carry nutrients away from concentrated «hotspots,» the team writes, has plummeted to eight percent of what it was in the past — before the extinction of some 150 species of mammal «megafauna» at the end of the last ice age.

The local diversity and unique geologic history (covered by neither glaciers nor oceans for the past 225 million years, the Ozarks provided refuge for migrating species during the Ice Age) explain the richness of the lichens here: some 600 named species, along with 30 recently discovered ones awaiting their official designation.

Look at the great ice ages of the past.

There have been several such transitions in the past, but one of the largest and most dramatic transitions happened at the end of the last Ice Age.

In the early 1990s, they re-created a history of the Earth's atmosphere throughout the past 400,000 years — a record of our planet's air during the past four ice ages.

See the RealClimate discussions of the Little Ice Age and Medieval Warm Period for explanations of why both the Viking colonization of Greenland and the freezing of the River Thames actually tells us relatively little about past climate change.

«The climate reconstructions for the past 2,000 years have led to a simplistic picture of a Medieval Warm Period and a Little Ice Age.

The WAIS Divide deep ice core WD2014 chronology — Part 1: Methane synchronization (68 - 31 ka BP) and the gas age — ice age difference Climate of the Past, 11, 153 - 173

The WAIS Divide deep ice core WD2014 chronology — Part 1: Methane synchronization (68 - 31 ka BP) and the gas age — ice age difference Climate of the Past, 11, 153 - 173 \ nBuizert, C., and 15 others.

Re 92 and 105: First I just want to reitterate more generally what 105 said — Milankovitch cycles have had climate signals, in ice ages or otherwise, — well probably ever since the Moon formed, although the signal from times past will not always reach us, but I've read of evidence of Milankovitch precession cycle forcing of monsoons in lakes in Pangea (PS over geologic time the periods of some of the Milankovitch cycles have changed as the Moon recedes from the Earth due to tides).

We calculate the WD gas age - ice age difference (Delta age) using a combination of firn densification modeling, ice - flow modeling, and a data set of d15N - N2, a proxy for past firn column thickness.

Marine sediment cores will reveal records of past glacial - interglacial cycles while lake sediments and peat cores will reveal climate records since the last ice age.

At this early stage of knowledge, what was being studied were the glacial periods within the past few hundred thousand years, during the current ice age.

Geologists knew of some fairly widespread glaciations in the past: there was an ice - age at the end of the Ordovician period, some 445 million years back and, going further back again, there were some huge, perhaps planet - wide glaciations in the Proterozoic eon.

Although it was not a true ice age, the term was introduced It is not uncommon to read that ice cores from the polar regions contain records of climatic change from the distant past.

The assessment examines the following content; global warming, the greenhouse effect / gases, natural and human causes of past climate change, evidence of the little ice age, features of tropical storms and the effects and response to tropical storms.

Evidence for the maximum lowering of sea level during successive ice ages over the past several millions of years is sparse.

Discover the amazing ice age giants of Australia's past, the mega fauna, as revealed by the fossils and view the models recreated from the bones found in the Victoria Fossil Cave.

There are echoes of this past however, and it was interesting when we included the George Bellows painting of ice floes in the Hudson River on the top floor, because that piece harkens a little bit to aspects of late 19th - century art and the age of American Impressionism, with artists like Childe Hassam and William Merritt Chase.

However, in periods in the past, say around 8,200 years ago, or during the last ice age, there is lots of evidence that this circulation was greatly reduced, possibly as a function of surface freshwater forcing from large lake collapses or from the ice sheets.

Could you let us know what these much greater stimuli of the past (10,000 years, i.e. after the last ice - age) are?

Demonstrate that warming in the past tells us that warming will continue into the future, despite the fact that a very similar trend in the opposite direction during the middle of the 20th century convinced so many that we were headed for another ice age.

It is my understanding that the previous ice ages have ended in the past by a forcing from changes in tilt of the earth (i.e. Milankovitch cycles).

During some of the warm periods between past ice ages, it has been as warm as, or warmer than, it is today.

Mike's work, like that of previous award winners, is diverse, and includes pioneering and highly cited work in time series analysis (an elegant use of Thomson's multitaper spectral analysis approach to detect spatiotemporal oscillations in the climate record and methods for smoothing temporal data), decadal climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both climate model simulations and observational data for a 50 - 70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measurements).

For example, the ice age — interglacial cycles that we have been locked in for the past few million years seem to be triggered by subtle changes in the earth's orbit around the sun and in its axis of rotation (the Milankovitch cycles) that then cause ice sheets to slowly build up (or melt away)... which changes the albedo (reflectance) of the earth amplifying this effect.

The paper, combining evidence of driftwood accumulation and beach formation in northern Greenland with evidence of past sea - ice extent in parts of Canada, concludes that Arctic sea ice appears to have retreated far more in some spans since the end of the last ice age than it has in recent years.

Having read the comments here and in Jones and Mann (2004) «Climate over past millennia», I have been reflecting on some of the comments about the hockey stick wrt the Medieval Warm Period (MWP) and the Little Ice Age (LIA).

The research, led by Chronis Tzedakis of University College, London, examined similarities between the current warm interval between ice ages and a particular point, around 780,000 years ago, during a past warm period known as Marine Isotope Stage 19.

See e.g. this review paper (Schmidt et al, 2004), where the response of a climate model to estimated past changes in natural forcing due to solar irradiance variations and explosive volcanic eruptions, is shown to match the spatial pattern of reconstructed temperature changes during the «Little Ice Age» (which includes enhanced cooling in certain regions such as Europe).

However, our fortune would last much longer than that: the Milankovitch cycles can be calculated over millions of years with astronomical precision (and incidentally be used to predict the beginning of all the past ice ages), and according to that, the next major climate change would arrive only in about 50,000 years.

So, we might have been past the warmest period of this most recent interglacial, and beginning a slow, multi-thousand year descent into a new ice age — until we changed the atmospheric composition.

A new analysis of the dramatic cycles of ice ages and warm intervals over the past million years, published in Nature, concludes that the climatic swings are the gyrations of a system poised to settle into a quasi-permanent colder state — with expanded ice sheets at both poles.

(Much of the glaciological literature on termination of large ice ages requires ice - sheet growth past a threshold size.)

The discovery in the mid 19th century that there had been ice ages in the distant past proved that climate could change radically over much of the globe, a change vastly beyond anything mere humans seemed able to cause.

I suspect that it looked OK in your view or you didn't check; «the paper i cited talks of the hiatus in global temperatures for the past 20 years or so, that the Little Ice Age was global in extent, and that climate models can not account for the observations we already have let alone make adequate predictions about what will happen in the future.

Let me just quote Jones and Mann: «««Medieval Warm Period» and «Little Ice Age» are therefore restrictive terms, and their continued use in a more general context is increasingly likely to hamper, rather than aid, the description of past large - scale climate changes.