I can’t comment on his blog, because the Askimet software has got me marked as a pest, and my comments go straight to spam. There is no facility for telling Askimet I’m OK, so there it is, I’m as good as banned. So I’ll make my comments here, which are in any case longer than is form for comments there.
The report predicts that half of the world’s identified tipping points – such as the collapse of polar ice sheets and the drying out of the Amazon rainforest – would be crossed under 2C warming, compared with 20% of them at 1.5℃.
The third record year in a row has been declared. The last time it was as hot as this was 115,000 years ago. The last time CO2 was this high was in the Pliocene, 3 to 5 million years ago when the temperature became roughly 3 to 4 degrees Celsius warmer than today, and the sea level up to 40 metres higher.
Andrew Simms for The Guardianpolled a number of scientists about whether we could keep warming under 2°C. Not a single one thought we would. One scientist said “not a cat in hell’s chance”. Kevin Anderson, now professor in Uppsala, said politically we gave up years ago. Prof Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research, would “only confirm that it is still possible to keep global warming below 2C”. Technically speaking, I assume. Continue reading Record 2016 heat spells trouble on global scale→
James Hansen worries that “we may be approaching a point of no return, a situation in which our children inherit a climate system undergoing changes that are out of their control, changes that will cause them irreparable harm”. He’s looked at the models, at current observations, and at what happened during the Eemian interglacial 118,000 years ago, and he doesn’t like what he sees.
During the Eemian, when global average temperatures were about 1°C more than now, sea level was about 3-4 metres higher than now for a considerable time. Then about 118,000 years ago, towards the end of the interglacial, it peaked at 6-9 meters, including a rise of 2-3 metres within several decades. A similar sea level rise of several metres now would see the inundation of many of the world’s major cities.
Back in 2011, we wrote about a fascinating new way to heat-treat regular, cheap steel to endow it with an almost miraculous blend of characteristics. Radically cheaper, quicker and less energy-intensive to produce, Flash Bainite is stronger than titanium by weight, and ductile enough to be pressed into shape while cold without thinning or cracking. It’s now being tested by three of the world’s five largest car manufacturers, Continue reading Climate clippings 160→
James Hansen has a 17 author paper out suggesting that we could have multi-metre sea level rise this century. It’s based on the notion that meltwater from the ice sheets interrupts ocean circulation patterns, which then cause a feedback loop via larger storms. I think that’s it in brief. Continue reading Climate clippings 148→
The ink is scarcely dry in the IPCC’s fifth report when it has become clear that they have badly underestimated the risks in two key areas – sea level rise and climate sensitivity. With respect to the latter, David Spratt at Climate Code Red comes to the conclusion that there is no carbon budget left, no ‘burnable carbon’ if we are looking for a safe climate.
As I said in Climate clippings 97 the fourth IPCC report in 2007 estimated that the planet will warm between 2 and 4.5°C warming in response to a doubling of the amount of CO2 in the atmosphere, with a best estimate of 3°C. This estimate was followed by a number of studies suggesting a lower sensitivity, leading the IPCC’s fifth report to extend the range to 1.5°C at the lower end and omit a best estimate entirely.
Back in May Dana Nuccitelli reported on a study by Kummer & Dessler which showed that recent studies suggesting an insensitive climate are flawed. They eliminate the lower part of the range but still converge on a value around 3°C.
Spratt now reports:
a recent paper by Sherwood, Bony et al looking at clouds and atmospheric convective mixing finds that on “the basis of the available data… the new understanding presented here pushes the likely long-term global warming towards the upper end of model ranges.” Taking “the available observations at face value,” they write, “implies a most likely climate sensitivity of about 4°C, with a lower limit of about 3°C.”
Problem is that these estimates are based on short-term feedbacks only, or what is known as Equilibrium Climate Sensitivity (ECS). Spratt says:
Paleoclimatology (study of past climates) suggests that if longer-term feedbacks of “slow” factors are taken into account, such as the decay of large ice sheets, changes in the carbon cycle (changed efficiency of carbon sinks such as permafrost and methane clathrate stores, as well as biosphere stores such as peatlands and forests), and changes in vegetation coverage and reflectivity (albedo), then the Earth’s sensitivity to a doubling of CO2 could itself be double that of the “fast” climate sensitivity predicted by most climate models, or around 6°C.
A measure of these effects for a doubling of CO2 is known as Earth System Sensitivity (ESS).
He says that “ESS is generally considered to come into play over periods from centuries to several millennia.”
If that’s how the earth system operates, that’s how we must operate.
Now in February 2013, new research on Russian cave formations measuring historic melting rates gives rise to a warning that a +1.5°C global rise in temperature compared to pre-industrial is enough to start a general permafrost melt.
Other research indicates that thaw and decay of permafrost carbon, once seriously started, is irreversible.
Rather than 2°C as a guardrail to avoid dangerous climate change, we must expect danger to occur at 1.5°C.
We are pushing the climate harder than it has been pushed in the last 65 million years. In this post I asked what does 4°C mean?
Professor John Schellnhuber, Director of the Potsdam Institute for Climate Impact Research, provides a stark assessment of the difference between a rise of two and four degrees. ‘The difference,’ he says, ‘is human civilisation. A 4°C temperature increase probably means a global [population] carrying capacity below 1 billion people’.
For a safe climate as we saw in The game is up, again quoting David Spratt:
We have to come to terms with two key facts: practically speaking, there is no longer a “carbon budget” for burning fossil fuels while still achieving a two-degree Celsius (2°C) future; and the 2°C cap is now known to be dangerously too high.
I hate to say this, but at the leading edge people are catching up with what James Hansen was saying back in 2008. Here’s a table from page 17 of the 2011 paper Earth’s Energy Imbalance and Implications where he gives four categories of climate sensitivity:
The fourth doesn’t bear thinking about. Clearly he’s a dangerous man and needs to be locked up.
In this post I’ve included a series of explanatory images of the Antarctic in order to assist understanding the peril we are in from changes there, and why the Antarctic is going to be central to the climate change story over the coming centuries. What happens to the grandchildren of those who are children now is the big concern. In large part these images relate to items 2-4 of Climate clippings 96.
These winds draw rain away from southern Australia, and isolate Antarctica to some extent in terms of atmospheric warming. But they also churn up the ocean, leading to deeper mixing of heat and greenhouse gases.
Both the deep and the shallow formations of the thermohaline circulation system wrap themselves around the Antarctic:
One way or another warm water is penetrating through to Antarctica. The underlying topography of Antarctica reveals much of the land lying below sea level:
The borderline between blue and green marks sea level. Warmer water is coming directly into contact with the ice sheet and chewing away at the bottom of the ice shelves which form plugs holding up vast quantities of ice in the glaciers stretching hundreds of kilometres inland. The following image shows how the continent drains:
There is concern now that West Antarctica has tipped and with East Antarctica also more vulnerable than previously thought, sea level rise of some metres is now inevitable even if we were to somehow instantly curb greenhouse emissions.
Greenland is quite a different problem. For starters the underlying topography is saucer shaped, with glaciers exiting to the sea through ‘gates’. This image shows the topography:
Greenland melts very much from the surface, so its largely a matter of meltwater penetrating, indeed plunging at times, through the surface to the rock below and glaciers speeding up. This image shows some people standing where I’d never stand:
This image shows melting covering the entire Greenland ice sheet for a few days in 2012:
The panel on the left shows a more typical summer melt pattern, which is advancing noticeably over short time frames of a few years.
In the Antarctic, this image shows surface warming over the period 1981-2007:
But with the average temperature around -39°C on the East Antarctic ice sheet, which is four kilometres high, that huge lump of ice is relatively stable. This image from NASA in 2005 shows significant perimeter surface melting around East Antarctica:
The new research sees concern that warmer sea waters may destabilise the ice further inland than previously thought. Match the red blobs on East Antarctica with the drainage map at Figure 4.
Of some some concern and some comfort is the Andrill Project which found that “the West Antarctic ice sheet has collapsed and regrown over 60 times in the past few million years”. This image shows what happened about a million years ago over a 12,000 year period:
Concern because the Andrill research shows what can happen with mild orbital forcing (the Milankovitch cycles) as the main driver. I understand that CO2 concentration back then was only 400 to 450 ppm, which is where we now, implying that we are already committed to wasting the West Antarctica ice sheet. There is some comfort, however, that a change in the orbital forcing, which is far weaker than what we are doing now, arrested the melt in West Antarctica and brought the ice sheet back again. There was no tipping point which saw the whole East Antarctic sheet disappear.
For perspective I’ll post one of my favourites, a graph from David Archer in 2006 showing the broad relationship between temperature and sea level:
Do not connect the dots with straight lines. Most importantly, I think we now stand at the upper level of a 2°C interval where the sea level did not change much. The NH continental ice sheets had disappeared and the remaining ones – Antarctica, Greenland and the Arctic – were not seriously in play. Even now the main sources of sea level rise lie elsewhere. This table (13.1 from the IPCC5 WG1 Technical Summary) shows what’s happening:
That’s hard to read, so here are the figures for the average annual expansion for 1993-2010:
Thermal expansion – 1.1mm
Glaciers except Greenland and Antarctica – 0.76mm
Glaciers in Greenland – 0.10mm
Greenland ice sheet – 0.33mm
Antarctic ice sheet – 0.27mm
With 4-5°C we can expect complete deglaciation and 75 to 80m sea level rise, made up of East Antarctica 59m, Greenland 6-7m, West Antarctica 5-6m, other glaciers and ice caps about 0.5m and thermal expansion, I don’t know, but I think in single figures. Greenland and Antarctica are accelerating rapidly and some time this century will become the top two contributors. These graphs from Skeptical Science are instructive:
Greenland and West Antarctica are in a death spiral of accelerating ice sheet decay. It’s happened 60 or more time before in recent paleo history. West Antarctica, being more vulnerable may overtake Greenland.
One could say from this that East Antarctica is not yet in play, but science seems to suggest it is not far away.
When ice sheet decay gets going Hansen sees it as possibly progressing in geometric fashion, producing a curve like this:
My thinking is that East Antarctica will tip sometime in the next decade, and that ice sheets will decay from there in a pattern that is more exponential than linear. Hansen’s scenario, which he puts forward as a serious possibility, does not look crazy.
I suspect that we are already committed to double digit sea level rise, and there’s not a thing we can do to prevent it; the question is when will it happen? We can only adapt and minimise.
I suspect also that things will go seriously pear-shaped during the latter part of this century. Pity our grandchildren’s grandchildren.
Update: There is a short ABC video news item about the Antarctic ice melt doubling since the last survey. At the end it says the process could take 1000 years. For a complete melt that would be lightning fast – 7.5 to 8 metres per century, or a metre every 12-13 years. We are pushing the system more than 10 times faster than it has ever been pushed before.