[LINK] "Carbon emissions 'will defer Ice Age'"

[rfmcdonald]

80 Beats' Veronique Greenwood has linked to a new study, reported by BBC News' Richard Black, suggesting that global warming--product of human industries--may have postponed the next Ice Age.

In the journal Nature Geoscience, they write that the next Ice Age would begin within 1,500 years - but emissions have been so high that it will not.

"At current levels of CO2, even if emissions stopped now we'd probably have a long interglacial duration determined by whatever long-term processes could kick in and bring [atmospheric] CO2 down," said Luke Skinner from Cambridge University.

Dr Skinner's group - which also included scientists from University College London, the University of Florida and Norway's Bergen University - calculates that the atmospheric concentration of CO2 would have to fall below about 240 parts per million (ppm) before the glaciation could begin.

The current level is around 390ppm.

Other research groups have shown that even if emissions were shut off instantly, concentrations would remain elevated for at least 1,000 years, with enough heat stored in the oceans potentially to cause significant melting of polar ice and sea level rise.
[. . .]

Using analysis of orbital data as well as samples from rock cores drilled in the ocean floor, Dr Skinner's team identified an episode called Marine Isotope Stage 19c (or MIS19c), dating from about 780,000 years ago, as the one most closely resembling the present.

The transition to the Ice Age was signalled, they believe, by a period when cooling and warming seesawed between the northern and southern hemispheres, triggered by disruptions to the global circulation of ocean currents.

If the analogy to MIS19c holds up, this transition ought to begin within 1,500 years, the researchers say, if CO2 concentrations were at "natural" levels.

As things stand, they believe, it will not.

The authors note that while human output of carbon dioxide may well have postponed an ice age, the amount being produced goes far beyond the minimum levels necessary to sustain our currently warm climate.

The UK lobby group the Global Warming Policy Foundation, for example, has flagged up a 1999 essay by astronomers Sir Fred Hoyle and Chandra Wickramasinghe, who argued that: "The renewal of ice-age conditions would render a large fraction of the world's major food-growing areas inoperable, and so would inevitably lead to the extinction of most of the present human population.

"We must look to a sustained greenhouse effect to maintain the present advantageous world climate. This implies the ability to inject effective greenhouse gases into the atmosphere, the opposite of what environmentalists are erroneously advocating."

Luke Skinner said his group had anticipated this kind of reception.

"It's an interesting philosophical discussion - 'would we better off in a warm [interglacial-type] world rather than a glaciation?' and probably we would," he said.

"But it's missing the point, because where we're going is not maintaining our currently warm climate but heating it much further, and adding CO2 to a warm climate is very different from adding it to a cold climate.

"The rate of change with CO2 is basically unprecedented, and there are huge consequences if we can't cope with that."