Sentences with phrase «occurred hundreds to thousands of years»

Not exact matches

Since similar estimates have been employed by various writers for at least fifteen years, it is obvious that no one is actually counting; that no one knows how many are involved; and that growth, if it is occurring at all, is not nearly so rapid as the growth of evangelical Christian communities, which seem to be expanding by hundreds of thousands every few years.

Even if the near future doesn't unfold like the 2004 climate - gone - haywire film The Day After Tomorrow, scientists need to be able to produce accurate models of what abrupt change (more likely spanning hundreds or thousands or years, rather than days) would look like and why it might occur, explains Zhengyu Liu, lead author of the study and director of the University of Wisconsin — Madison's Center for Climate Research.

Volumes range from a few hundred cubic metres to more than a thousand cubic kilometres, and the larger ones can travel for hundreds of kilometres although none on that scale have occurred for several hundred thousand years.

Because it takes hundreds of thousands of years for the genetic evolution of natural selection to occur, these sex differences in navigation strategies probably have their roots in the Stone Age.

While this study focuses on how tragic cardiac arrest might be when it strikes an athlete, Dr. Kudenchuk emphasizes that it also typifies the bystander inaction that occurs in hundreds of thousands of instances of others who fall victim to out - of - hospital cardiac arrest each year across the globe.

Small eruptions that erupt less than one cubic kilometre of material occur very frequently (daily to yearly), whilst the largest eruptions that erupt hundreds of cubic kilometres of material are infrequent, with hundreds of thousands of years between them.

To the North there are black sand volcanic beaches, the color of which is the result of volcanic eruptions occurring hundreds and thousands of years ago.

Rather, excess CO2 returns toward baseline at a multitude a different rates, with chemical equilibration in the ocean occurring over decades (depending on depth), ocean carbonate buffering through sediment dissolution requiring centuries to millennia, and eventual restoration of carbonate sediment levels by terrestrial weathering occurring over hundreds of thousands of years — a long «tail» that can account for as much as 20 to 40 percent of CO2 excess in the estimates described by David Archer et al in CO2 Atmospheric Lifetimes.

However, substantial ice sheet changes that occurred during the last hundreds to few thousands of years remain poorly quantified and are not included in our model.

It has therefore occurred to a number of climatologists that perhaps by studying the past (tens of thousands of years ago to hundreds of millions of years ago) and seeking relationships between CO2 and climate during those periods, we might be able to obtain real world data on how climate and CO2 are connected.

The second question is, postulating that the temperature record from satellites is absolutely accurate and unfudged, and in light of the fact that climate changes historically occur naturally with periods of hundreds to thousands of years, do you think that the 31 annual data points available from the satellite record are adequate to establish long term climate trends and that the trends are a consequence of human activity?

Only one of the past «Big Five» mass extinctions (the dinosaur extinction event at the end of the Cretaceous) is thought to have occurred as rapidly as would be the case if currently observed extinctions rates were to continue at their present high rate (Alvarez et al., 1980; Barnosky et al., 2011; Robertson et al., 2004; Schulte et al., 2010), but the minimal span of time over which past mass extinctions actually took place is impossible to determine, because geological dating typically has error bars of tens of thousands to hundreds of thousands of years.

However, the Big Five occurred over periods of hundreds of thousands to millions of years, so Barnosky and colleagues also attempted to determine how long it might take us to reach mass extinction levels (75 % of species extinct).

To answer this question, the scientists examined a hypothetical scenario in which the Big Five extinctions occurred suddenly, such that all of the species went extinct over just 500 years rather than over hundreds of thousands to millions of yearTo answer this question, the scientists examined a hypothetical scenario in which the Big Five extinctions occurred suddenly, such that all of the species went extinct over just 500 years rather than over hundreds of thousands to millions of yearto millions of years.