Nicholas Stern writes: The Intergovernmental Panel on Climate Change last September pointed to a changing pattern of extreme weather since 1950, with more heatwaves and downpours in many parts of the world, as the Earth has warmed by about 0.7C.
The IPCC has concluded from all of the available scientific evidence that it is 95% likely that most of the rise in global average temperature since the middle of the 20th century is due to emissions of greenhouse gases, deforestation and other human activities.
The upward trend in temperature is undeniable, despite the effects of natural variability in the climate which causes the rate of warming to temporarily accelerate or slow for short periods, as we have seen over the past 15 years.
If we do not cut emissions, we face even more devastating consequences, as unchecked they could raise global average temperature to 4C or more above pre-industrial levels by the end of the century.
This would be far above the threshold warming of 2C that countries have already agreed that it would be dangerous to breach. The average temperature has not been 2C above pre-industrial levels for about 115,000 years, when the ice-caps were smaller and global sea level was at least five metres higher than today.
The shift to such a world could cause mass migrations of hundreds of millions of people away from the worst-affected areas. That would lead to conflict and war, not peace and prosperity.
In fact, the risks are even bigger than I realised when I was working on the review of the economics of climate change for the UK government in 2006. Since then, annual greenhouse gas emissions have increased steeply and some of the impacts, such as the decline of Arctic sea ice, have started to happen much more quickly.
We also underestimated the potential importance of strong feedbacks, such as the thawing of the permafrost to release methane, a powerful greenhouse gas, as well as tipping points beyond which some changes in the climate may become effectively irreversible.
What we have experienced so far is surely small relative to what could happen in the future. We should remember that the last time global temperature was 5C different from today, the Earth was gripped by an ice age.
So the risks are immense and can only be sensibly managed by reducing greenhouse gas emissions, which will require a new low-carbon industrial revolution. [Continue reading…]
“We also underestimated the potential importance of strong feedbacks, such as the thawing of the permafrost to release methane, a powerful greenhouse gas, as well as tipping points beyond which some changes in the climate may become effectively irreversible.”
This is a huge unknown. There are estimated to be around 150,000 methane seeps in the Alaska alone. There are also vast stores of trapped methane in the Arctic in the form of gas hydrates. With the break down of the cyrosphere we could indeed see a disaster scenario unfolding with untold spin-off effects.
We see two opposing human responses to scientific uncertainty. The scientists urge caution adn preemptive steps to mitigate (if not turn around) the process of constantly worsening climate change. they say, we really don’t know all the variables, all the processes, all teh facts, so we shoudl be exta cautious.
The industrialists, some religious folks, and many know-nothings of various stripes, say, well all this is uncertain, so it is too soon to take costly steps by way of mitigation. Let us wait until it is KNOWN and IRREFUTABLE that climate change is happening, is bad, adn can be turned around by human effort. (“What, me worry?”)
That is like waiting to treat cancer untl it is in Stage-4. There are thigs that, if they are to be done, should be done quickly and expeditiously. Reacting to climate change is one such.