Sentences with phrase «during past ice ages»

As massive ice sheets retreated during past ice ages, their weight on the land below lifted and the land rebounded.

Seafloor sediments show that during past ice ages, more iron - rich dust blew from chilly, barren landmasses into the oceans, apparently producing more algae in these areas and, presumably, a natural cooling effect.

This line marks a deep ocean channel that remained water - filled even during past ice ages, when sea levels saw channels between other islands in the region dry out.

Costa and her colleagues wanted to find out if the dusty atmosphere also stimulated CO2 sequestration in other ocean basins during the past ice age.

As Weir points out, it likely owes its survival as a species on being geographically isolated from its parental species at some point during a past ice age when rainforest coverage contracted, and wide rivers formed natural barriers.

Like other sea - holes or «vertical caves,» the Great Blue Hole in Belize's Lighthouse Reef actually formed on dry land, during a past ice age when the sea level was a lot lower than it is today.

Not exact matches

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 research takes as its desired stable state the Holocene epoch, the 10,000 years since the last ice age during which human civilization has flourished, and attempts to identify the key variables that might push planetary cycles past safe thresholds.

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).

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.

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.

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.

During the ice age, a woolly mammoth loner with a tragic past joins a wisecracking sloth and a scheming saber toothed tiger on a dangerous journey to reunite a one year old boy with his hunter father.

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

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.

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.

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

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).

While the conditions in the geological past are useful indicators in suggesting climate and atmospheric conditions only vary within a a certain range (for example, that life has existed for over 3 billion years indicates that the oxygen level of the atmosphere has stayed between about 20 and 25 % throughout that time), I also think some skeptics are too quick to suggest the lack of correlation between temperature and CO2 during the last 550 million years falsifies the link between CO2 and warming (too many differences in conditions to allow any such a conclusion to be drawn — for example the Ordovician with high CO2 and an ice age didn't have any terrestrial life).

Scientists who have studied past phases of climate change have found that iron dust may have caused similar effects during ice ages and are hoping to replicate those without causing unwanted fallout.

All of Norway's glaciers completely disappeared at least once, 11,39 and Greenland's greatest glaciers, like the Jakobshavn, remained much further inland than now observed.29 Like many northern glaciers, Jakobshavn had only recently advanced past its present terminus during the unprecedented cold of the Little Ice Age.

Conversely, during low solar activity during the Little Ice Age, transport of warm water was reduced by 10 % and Arctic sea ice increased.17 Although it is not a situation I would ever hope for, if history repeats itself, then natural climate dynamics of the past suggest, the current drop in the sun's output will produce a similar cooler climate, and it will likely be detected first as a slow down in the poleward transport of ocean heat.22 Should we prepare for this possibiliIce Age, transport of warm water was reduced by 10 % and Arctic sea ice increased.17 Although it is not a situation I would ever hope for, if history repeats itself, then natural climate dynamics of the past suggest, the current drop in the sun's output will produce a similar cooler climate, and it will likely be detected first as a slow down in the poleward transport of ocean heat.22 Should we prepare for this possibiliice increased.17 Although it is not a situation I would ever hope for, if history repeats itself, then natural climate dynamics of the past suggest, the current drop in the sun's output will produce a similar cooler climate, and it will likely be detected first as a slow down in the poleward transport of ocean heat.22 Should we prepare for this possibility?

In the past 400, maybe, but then that means Mann's data only shows that things are warmer then they were during the Little Ice Age.

This also explains why, as you point out, CO2 levels have in the past been high during an ice age (although never at 5000ppm — the late - Ordovician would have been a contender but this recent paper — ttp: / / geology.gsapubs.org/content/37/10/951.abstract — demonstrates that CO2 consumption increased during the mid-Ordovician as a result of continental weathering, however levels were held up by volcanic outgassing.

For roughly the past 10,000 years, since the end of the last Ice Age, human beings have enjoyed a relatively stable, comfortable «interglacial» period, during which they've invented everything from agriculture to moon rockets.

report that ocean sediment cores containing an «undisturbed history of the past» have been analyzed for variations in PP over timescales that include the Little Ice Age... they determined that during the LIA the ocean off Peru had «low PP, diatoms and fish,» but that «at the end of the LIA, this condition changed abruptly to the low subsurface oxygen, eutrophic upwelling ecosystem that today produces more fish than any region of the world's oceans... write that «in coastal environments, PP, diatoms and fish and their associated predators are predicted to decrease and the microbial food web to increase under global warming scenarios,» citing Ito et al..

Sea - level rise during past warm periods IPCC faq: «What caused the ice ages...?»

There is ample circumstantial evidence that it has a significant impact, such as the Little Ice Age that occurred during the last grand minimum, as well as the unusually cold climates that also matched past weak cycles, now, and also in the early 19th and 20th centuries.

For the past 400,000 years, pH rose to about 8.35 during the depths of each ice age.

Responding to and in the manner of KK Tung's UPDATE (and, you can quote me): globally speaking the slowing of the rapidity of the warming, were it absent an enhanced hiatus compared to prior hiatuses, must at the least be interpreted as nothing more than a slowdown of the positive trend of uninterrupted global warming coming out of the Little Ice Age that has been «juiced» by AGW as evidenced by rapid warming during the last three decades of the 20th Century, irrespective of the fact that, «the modern Grand maximum (which occurred during solar cycles 19 — 23, i.e., 1950 - 2009),» according to Ilya Usoskin, «was a rare or even unique event, in both magnitude and duration, in the past three millennia [that's, 3,000 years].»

Studies in the past have also confirmed the value of this feedback on the AIS evolution during the ice age.

As I have stated publicly on many occasions, there is no definitive scientific proof, through real - world observation, that carbon dioxide is responsible for any of the slight warming of the global climate that has occurred during the past 300 years, since the peak of the Little Ice Age.

Here, we argue that the twentieth and twenty - first centuries, a period during which the overwhelming majority of human - caused carbon emissions are likely to occur, need to be placed into a long - term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist.

Of for pete's sake, Gavin is only saying that the paleo record during just the past few ice age cycles seems to constrain the «sensitivity of CO2 to temperature» to far less than what Salby seems to be implying.

Related Volcanoes, Tree Rings, and Climate Models: This is how science works Fossil Focus: Using Plant Fossils to Understand Past Climates and Environments Atmospheric oxygen over Phanerozoic time Coupled carbon isotopic and sedimentological records from the Permian system of eastern Australia reveal the response of atmospheric carbon dioxide to glacial growth and decay during the late Palaeozoic Ice Age

In fact, if humankind was really as dumb as the fans of DPS would have us believe, we wouldn't be around today to hear their doomsaying, because Homo sapiens would have been wiped out during vastly larger environmental swings (in and out of ice ages, for example) in our past, than those expected as a consequence of the burning of fossil fuels to produce the energy that powers our world — a world in which the human life expectancy, perhaps the best measure of our level of «dumbness» or «smartness» — has more than doubled over the last century and continues to grow ever longer.

The models heavily relied upon by the Intergovernmental Panel on Climate Change (IPCC) had not projected this multidecadal stasis in «global warming»; nor (until trained ex post facto) the fall in TS from 1940 - 1975; nor 50 years» cooling in Antarctica (Doran et al., 2002) and the Arctic (Soon, 2005); nor the absence of ocean warming since 2003 (Lyman et al., 2006; Gouretski & Koltermann, 2007); nor the onset, duration, or intensity of the Madden - Julian intraseasonal oscillation, the Quasi-Biennial Oscillation in the tropical stratosphere, El Nino / La Nina oscillations, the Atlantic Multidecadal Oscillation, or the Pacific Decadal Oscillation that has recently transited from its warming to its cooling phase (oceanic oscillations which, on their own, may account for all of the observed warmings and coolings over the past half - century: Tsoniset al., 2007); nor the magnitude nor duration of multi-century events such as the Mediaeval Warm Period or the Little Ice Age; nor the cessation since 2000 of the previously - observed growth in atmospheric methane concentration (IPCC, 2007); nor the active 2004 hurricane season; nor the inactive subsequent seasons; nor the UK flooding of 2007 (the Met Office had forecast a summer of prolonged droughts only six weeks previously); nor the solar Grand Maximum of the past 70 years, during which the Sun was more active, for longer, than at almost any similar period in the past 11,400 years (Hathaway, 2004; Solankiet al., 2005); nor the consequent surface «global warming» on Mars, Jupiter, Neptune's largest moon, and even distant Pluto; nor the eerily - continuing 2006 solar minimum; nor the consequent, precipitate decline of ~ 0.8 °C in TS from January 2007 to May 2008 that has canceled out almost all of the observed warming of the 20th century.

There is no comparison between «it was colder during the little ice age and warmer during the medieval warm period than the consensus claims» and the consensus claims to knowledge about temperatures current and past.

On the one side, we know that the level of carbon dioxide in the atmosphere was much lower during past ice - ages than during warm periods, so it is reasonable to expect that an artificially high level of carbon dioxide might stop an ice - age from beginning.

Argues that the twentieth and twenty - first centuries, a period during which the overwhelming majority of human - caused carbon emissions are likely to occur, need to be placed into a long - term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist