January 13, 2016

expert reaction to research on ice ages and human impacts

A group of researchers have published their work in the journal Nature which reports that, based on their modelling, atmospheric carbon dioxide can influence timings of ice ages. Following this they also suggest that carbon dioxide emissions from human activity may delay the next ice age by 100,000 years.

Prof. Andrew Watson FRS, Royal Society Research Professor at the University of Exeter, said:

“This study further confirms what we’ve suspected for some time, that the carbon dioxide humans have added to the atmosphere will alter the climate of the planet for tens to hundreds of thousands of years, and has cancelled the next ice age. Earth has gone through a series of many such ice ages over the last million years, and the low natural concentrations of carbon dioxide was a necessary condition for that to happen.

“Humans now effectively control the climate of the planet. If only we were wise enough to be able to use that power responsibly, this might be a good thing, as a planet that avoided major ice ages would probably be better for most of the species living on it. Unfortunately, I don’t think we’ve reached that level of wisdom yet.”

Prof. Richard Allan, Professor of Climate Science at the University of Reading, said:

“Ice age cycles are caused by regular changes in Earth’s orbit around the sun over tens to hundreds of thousands of years, the size of which is amplified by knock on effects including changes in ice coverage and natural responses in CO2.

“Earth’s orbit around the sun is oval in shape but this becomes more circular every hundred thousand years and more particularly so every 400 thousand years. Our current mild interlude coincides with a near circular orbit like the one 400 thousand years ago when the mild interglacial lasted longer than usual. We know that our current warm period will last many tens of thousands of years even without elevated concentrations of greenhouse gases associated with human activity.

“The many tens of thousands of years after which the next ice age may commence is very long compared to the appearance of modern human societies and is therefore not worth worrying about compared to immediate concerns about damaging human-caused climate change expected over the coming decades if no action is taken to mitigate this likelihood.”

Prof. Eric Wolff FRS, Royal Society Research Professor at the University of Cambridge, said:

“This is an interesting piece of work that adds some solid (model) evidence to existing ideas.  There have been previous papers suggesting that the next ice age is many tens of thousands of years away, and that the combination of seasonal solar energy at the latitude where an ice sheet would form, plus CO2, is what determines the onset of an ice age.  But this paper goes much further towards quantifying where the limits are. It represents a nice confirmation that there is a relatively simple way of estimating the combination of insolation and CO2 to start an ice age.

“I think it’s important to note that the authors show that we would not have started an ice age at the last insolation minimum even at CO2 concentrations somewhat below the pre-industrial (280 ppm). So, while humans have started to control many aspects of the climate and environment, the fact that we are not yet in an ice age can probably not be laid at our door.  At the moment we seem to be lucky that an ice age wasn’t quite coming anyway.”

Dr Ed Hawkins, Climate research scientist at the University of Reading, said:

“There is a long history of trying to understand the causes of ice ages. Much of the early work on the greenhouse effect in the 19th century was aimed at understanding the natural factors that might cause global temperatures to rise and fall so much.

“The question of whether human activity might reduce the chance of returning to an ice age was famously discussed in 1938 by Guy Callendar, who wrote that ‘the return of the deadly glaciers should be delayed indefinitely’ by the increase in global temperatures due to greenhouse gas emissions.  Unfortunately, the harmful impacts of that same temperature rise for the here and now are well documented.”

Prof. Jonathan Bamber, Director of the Bristol Glaciology Centre, University of Bristol, said:

“Ice Ages are a recurrent phenomenon caused by subtle changes in the orbit of the Earth around the Sun.  We are currently 12,000 years into a warm interglacial period that normally lasts about 20-30 thousand years. This new research suggests that human-induced climate change could delay the onset of the next Ice Age by 100,000 years.

“It is both remarkable and a little scary to think that, in a short space of time, humans have been able to modify the climate system in such a dramatic and profound way.”

Prof. Chris Rapley, Professor of Climate Science at University College London, said:

“This is an interesting result that provides further evidence that we have entered a new geological era – ‘The Anthropocene’ – in which human actions are affecting the very metabolism of the planet.

“Humans have always interfered at the landscape scale (RIP the Woolly Mammoth), but our influence is increasingly of fundamentally a different character, and much more profound. Having said that, the suppression of an ice age is not as directly significant as the enhanced warming of what would otherwise have been a gently cooling planet.

“The consequences for agriculture, wildfires, water availability and extreme weather events are slowly playing out, but we know already that sea level rise, which had been static for several thousand years, is already progressing at a rate which is geologically significant – about a fifth of the sustained rate that occurred in the transition from the last ice age to the current interglacial.  Even if there were no further acceleration, sea level rise will ultimately cause humans to abandon coastal infrastructure, land areas and key parts of cities which are currently integral to the functioning of the world with which we are familiar.  All the more reason to take the agreement at COP21 in Paris seriously and accelerate efforts to turn words into actions.”

‘Critical insolation–CO2 relation for diagnosing past and future glacial inception’ by A. Ganopolski et al. published in Nature on Wednesday 13th January,. 

Declared interests

None declared