Even if humanity stopped emitting greenhouse gases tomorrow, Earth will warm for hundreds of years to come back and oceans will rise by metres, in keeping with a controversial modelling study published Thursday.
Natural drivers of world warming - more heat-trapping clouds, thawing permafrost, and shrinking sea ice - already set in motion by carbon pollution will tackle their own momentum, researchers from Norway reported within the Nature journal Scientific Reports.
"According to our models, humanity is beyond the point-of-no-return when it involves halting the melting of permafrost using greenhouse emission cuts because the single tool," lead author Jorgen Randers, a professor emeritus of climate strategy at the BI Norwegian grad school, told AFP.
"If we would like to prevent this melting process we must do something additionally - as an example, suck CO2 out of the atmosphere and store it underground, and make Earth's surface brighter."
Using a stripped-down climate model, Randers and colleague Ulrich Goluke projected changes resolute the year 2500 under two scenarios: the moment cessation of emissions, and therefore the gradual reduction of planet-warming gases to zero by 2100.
In an imaginary world where carbon pollution stops with a flip of the switch, the earth warms over the subsequent 50 years to about 2.3 degrees Celsius above pre-industrial levels - roughly half-a-degree above the target set within the 2015 Paris Agreement - and cools slightly then.
Earth's surface today is 1.2C hotter than it had been within the mid-19th century when temperatures began to rise.
But starting in 2150, the model has the earth getting down to gradually warm again, with average temperatures climbing another degree over the subsequent 350 years, and sea levels increasing by a minimum of three metres.
Under the second scenario, Earth heats up to levels that will tear at the material of civilisation way more quickly but finish up at roughly the identical point by 2500.
Tipping points
The core finding - contested by leading climate scientists - is that several thresholds, or "tipping points", in Earth's climate system have already been crossed, triggering a self-perpetuating process of warming, as went on ample years within the past.
One of these drivers is the rapid retreat of sea ice within the Arctic.
Since the late 20th century, immeasurable square kilometres of snow and ice - which reflects about 80 per cent of the Sun's radiative beat back into space - is replaced in summer by open ocean, which absorbs the identical percentage instead.
Another source is the thawing of permafrost, which holds twice the maximum amount of carbon as there's within the atmosphere. The third is increasing amounts of vapour, which also contains a warming effect.
Reactions from half-a-dozen leading climate scientists to the study - which the authors acknowledge is schematic - varied sharply, with some saying the findings merit follow-up research, et al rejecting it out of hand.
"The model used here is .. not shown to be a reputable representation of the 000 climate system," said Richard Betts, head of climate impacts research at the University of Exeter.
"In fact, it's directly contradicted by competent and extensively evaluated climate models."
Mark Maslin, a professor of clim tology at University College London, also pointed to shortcomings within the model, referred to as ESCIMO, describing the study as a "thought experiment."
"What the study does draw attention to is that reducing global carbon emissions to zero by 2050" - a goal championed by the UN and embraced by a growing number of nations - "is just the beginning of our actions to accommodate temperature change."
Even the more sophisticated models utilized in the projections of the UN's scientific advisory body, the IPCC, show that the Paris climate pact temperature goals can't be reached unless massive amounts of CO2 are aloof from the atmosphere.
One way to try and do that's planting billions of trees. Experimental technologies have shown that sucking CO2 out of the air may be done mechanically, but thus far not at the size required.
No comments:
Post a Comment