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UK Scientific Adviser: Adaptation to Global 4ºC Temperature Rise May Be Necessary

by Jack Rosebro

Comparison of non-mitigation greenhouse gas emissions scenarios with actual reported emissions, 1990-2006. Click to enlarge. Source: Global Carbon Project (2007).

In an interview last week with The Guardian, Bob Watson, chief scientific adviser to the UK’s Defra (Department for the Environment, Food and Rural Affairs), warned that although his government should continue to work towards limiting the average global temperature increase to no more than 2ºC (3.6ºF) above pre-industrial levels, it should nevertheless prepare to adapt to as much as a 4ºC (7.2ºF) increase.

Watson’s words represent one of the first statements by a ranking scientific adviser to an industrialized country that a global temperature increase of no more than 2ºC—previously regarded by many experts, governments, and international bodies as the definitive “line in the sand” against climate change—may no longer be attainable.

Although a limit of 450ppm CO2 is one of the more ambitious emissions targets proposed by governments and corporations, the Intergovernmental Panel on Climate Change (IPCC) estimates that even at that limit, there is a 20% likelihood that global temperatures will increase by 3.5ºC or more. Watson’s statement has received support from Sir David King, the UK’s former chief scientist.

Even if we get the best possible global agreement to reduce greenhouse gases on any rational basis, you should be preparing for a 20% risk, so I think Bob Watson is quite right. My own feeling is that if we get to a four degree rise, it is quite possible that we would begin to see an runaway increase.

—Sir David King

Abrupt Climate Change

The potential for abrupt rather than gradual climate change has been receiving increased attention in recent years, in part because of accelerated changes in warming indicators such as Arctic sea ice, as well as improved data on past abrupt climactic events. In 2005, Defra sponsored the international symposium Avoiding Dangerous Climate Change, at the invitation of then British Prime Minister Tony Blair, at the Met Office in Exeter. A collection of scientific papers presented at the symposium were later published in book form.

In the introduction to that book, the lead authors wrote “...the primary changes in climate and sea level will be relatively slow and steady (albeit much faster than anything previously experienced by mankind). However, superimposed on these trends, there may well be abrupt and possibly irreversible changes that would have far more serious consequences”—in particular, the deterioration of two of the world’s great ice sheets, West Antarctica and Greenland, as well as the destabilization of the North Atlantic Ocean Thermohaline Circulation (THC), which is part of what is known as the “ocean conveyer belt.”.

Among the papers presented at the symposium was a report from the World Wildlife Fund (WWF) that projected a warming of 3.2 to 6.6ºC (5.76 to 11.88ºF) in the Arctic if the rest of the world warmed by 2ºC.

Tipping Elements

The debate over appropriate greenhouse gas reduction targets has become complicated by the specter of tipping elements—root causes of potentially sudden and catastrophic climate shifts—in response to rising temperatures worldwide. The concept was discussed a decade ago by climatologist Stephen Schneider of Stanford University, who termed such shifts “imaginable surprises.” The phrase “tipping elements”[*], most notably used in last year’s research paper Tipping elements in the Earth’s climate system, reflects increasing concern over the possibility of eight collapsing ecosystems:

  • Melting of Arctic sea-ice;
  • Decay of the Greenland ice sheet (GIS) ice volume;
  • Decay of the West Antarctic ice sheet (WAIS) ice volume;
  • Overturning of the Atlantic Ocean thermohaline cycle;
  • Increased amplitude of the El Niño - Southern Oscillation (ENSO);
  • Reduced rainfall during the Indian Summer Monsoon;
  • Dieback of the Amazon rainforests; and
  • Dieback of the boreal forest.

Research conducted by the authors of the paper has indicated, for example, that a 3 to 4ºC warming would trigger sufficient lengthening of the dry season to destabilize the Amazon forest in such a way that it would be unlikely to return, even if the warming trend was later reversed. “The fate of the Amazon,” they point out, “may be determined by a complex interplay between direct land-use change and the response of regional precipitation and ENSO to global forcing.” A ninth potential ecosystem shift, the greening of the Sahara-Sahel deserts, represents “a rare example of a beneficial potential tipping element.”

Uncertainty about physical processes that could trigger tipping elements underlies the ability of science to predict their likelihood. “Our short list differs from that of the IPCC,” notes the authors, “because our definition and criteria differ from, and are more explicit than, the IPCC notion of abrupt climate change. The evidence base we use is also slightly different because it encompasses some more recent studies.” Lesser potential tipping elements include the Antarctic Bottom Water, permafrost, marine methane hydrates, ocean anoxia, and Arctic ozone.

Average global temperatures have already increased by around 0.8ºC from 1850 to 2005, according to the UK Meteorological Office, with the warming trend from 1956 to 2005 (approximately 0.13ºC per decade) nearly twice as much as for the 100 years from 1906 to 2005.

In 2006, the Stern Review on the Economics of Climate Change (earlier post) estimated that a 4ºC increase in average global temperatures could result in the decimation of one-fifth to one-half of the world’s species, and 7 million to 300 million people affected by coastal flooding worldwide. Lord Nicholas Stern has remarked in recent months that the review now appears to have significantly underestimated the “speed of climate change.” (Earlier post.)

In April, James Hansen of NASA called for a global target of 350ppm CO2 (earlier post), saying to The GuardianIf you leave us at 450ppm for long enough it will probably melt all the ice—that’s a sea rise of 75 metres. What we have found is that the target we have all been aiming for is a disaster—a guaranteed disaster.

4ºC and the IPCC Report

One of the most aggressive reference scenarios used by the IPCC to model projected emissions prior to adjustment for mitigation measures, “A1 Fossil Intensive” (A1FI), projects a potential 4ºC rise in global temperatures by 2100 (earlier post). However, that scenario is already being outpaced by actual emissions as reported by governments. In addition, recent research indicates that some of those reports, especially emissions inventories from emerging economies, may be too optimistic (earlier post).

Although the modeling of a particular emissions scenario does not of itself indicate the likelihood of that scenario, 118 out of 177 emissions scenarios evaluated in the IPCC’s 2007 Fourth Assessment Report project a 3.2 to 4.0ºC increase. The report also cautions that non-linear climate feedbacks such as ice cover and carbon cycle changes may well lead to larger uncertainties for greater warming levels.

Classification of recent greenhouse gas stabilization scenarios according to different stabilization targets. Click to enlarge. Source: IPCC AR4

In the interview, King also mentioned that the turning point for the UK government with regard to climate change was not the Stern Review, but a 2004 report by the government’s Foresight program, which projected potential costs of defending Britain’s coasts against sea- level rise, as well as the possibility of abandoning some lands to the sea.

Under every scenario,” wrote the authors of UK Foresight’s Future Flooding report more than four years ago, “our analysis suggests that if current flood-management policies remain unchanged, the risk of flooding and coastal erosion will increase greatly over the next 30 to 100 years.

[*] The term “tipping elements,” which focuses on ecosystems that could be pushed into qualitatively different states of operation by human activity, is distinguished from the more common term “tipping points, ” which usually describes specific points in time during which disruptive change might occur.




According to some commentators A complete reading of all the scientific reports state " 0.8 degrees describes a real (accumulated)increase of 2o in the medium case in the moderate feedback case.
2 3 and 4 degree C really means 8 o."

2 o is catastrophic. When all the moderate scenario feed backs are played out.
3 to 4 are rated unsurvivable.

These numbers are considered 'moderate'

I think most of us are aware that the evidence based outcomes cannot be described as having followed the median line with even the most generous interpretation.

Hansen is not "out there" just a bit ahead of the pack.
The real issue is that most (govt advisers economists etc) readers of published reports focus on the first numbers sets.

He also suggests that 325ppm as an acceptable sustainable upper range. Still not an ideal long term option. 315ppm will bring us back to 1989 polar and other glacial, permanent, etc ice levels.

This very article appears to be quoting Hansen as greenlighting 350 ppm.
If you were to ask him, he would say he is being misquoted

We don't hear in the mass media that all the reports then go on to give a second set of numbers that describe the implications.
It is those 'Implied' numbers that describe the real situation.



Please state your meaning of the word 'unsurvivable'.

Unsurvivable by who or what exactly?


About 90 something percent of living creatures over the next 100 or so years.
Acording to historical fossil climate matching data.


I guess you can comprehend catastrophic.


Tuvalu, Bangladesh, iron filings are cheap, container ships.... I think there could be some unilateral decisions made in the near future by the low countries.


arnold: About 90 something percent of living creatures over the next 100 or so years.

"Both measurements and models show considerable uncertainty and variation; however, all point to carbon dioxide levels in the past that have been significantly higher than they are at present."

So Arnold, how is it that we are here at all if your theory is right?


1: It's not my theory.
It is my understanding (reading) of the science, much as I wish It wasn't.
The scientists in their numerous fields are themselves having to sit back and watch the markers pass.
IE certain Arctic ice conditions not expected till the end of he century are now expected within decades. Possibly by 2015.
That one being the expected sea ice free North West passage for the first time in human existence.
This is the flavour of commentary from our best and brightest scientists in their respective fields, although I'm sure some will go to the grave arguing against the whole thing.

2: The past you refer to predates *spammed again* sapien.

3: The previous planetary experiences/ conditions that resemble the present conditions have never occurred at anything like the rate of change we are experiencing.

4: No credible body is saying that past extinctions were caused by AGW. Or weren't caused by natural occurrence.

They are saying the present trajectory or rate of change is faster than anything seen before. So adaption for most species which cannot find new territory in pretty well any time frame (largely because we have caused disconnection to their ranges) is not an option.


This idea of rate of change is one that I think is most misunderstodd. Sure if you go back in history you can find evidence of CO2 levels, ice coverage and elevated temperatures in excess of what we see or project today.

The point is in the past most changes either a) occurred at a rate that life on the planet could adapt to, or more importantly b) when mass extinctions occurred it was not *our* (you, me personally) selves or our food chain that was being extincted by change that was too fast for evolution to keep up with. When it is personal we will care a lot more.


arnold: It's not my theory.

As far as I am concerned, it is your theory until you prove otherwise, since it is not passing a simple smoke test yet.

For example:

You initially say that your theory is "Acording to historical fossil climate matching data."

I present evidence that the "fossil climate matching data" shows significantly higher CO2 levels in the distant past.

Now your theory changes: The previous planetary experiences/ conditions that resemble the present conditions have never occurred at anything like the rate of change we are experiencing.

How do you reconcile this statement with your previous one? If what is happening today has never happened before, then the fossil evidence can't possibly support your theory.

You also now say that The past you refer to predates *spammed again* sapien. and No credible body is saying that past extinctions were caused by AGW. Or weren't caused by natural occurrence.

Relevance? As far as physical reality is concerned, CO2 is CO2. Whether it comes from the bottom of the ocean, or a volcano, or the tailpipe of a car, it will do its sinister work just the same.


DC: occurred at a rate that life on the planet could adapt to,

I don't understand this argument either. Consider this:

"The ice core showed the Northern Hemisphere briefly emerged from the last ice age some 14,700 years ago with a 22-degree-Fahrenheit spike in just 50 years, then plunged back into icy conditions before abruptly warming again about 11,700 years ago."

+12C in a few decades! Why aren't we dead?

richard schumacher

So forget about extinctions: if the temp goes up 4'C the ice sheets will slide into the sea, and sea level will go up 7 meters. What do you suppose it would cost to build 10 meter tall sea walls around every coastal area we want to keep and abandon the rest, and to accommodate a half-billion refugees?


Makes me more glad to live in Denver every day -- even the hot ones.


The water in the North Atlantic ocean is being reported at an increase of about +4C in the last 12 months or so.

Concurrently, we had 500 cm instead of 250 cm of snow last winter, which extended to also 6 months instead of four.

During the current warmer seasons, rain has been falling for about 22 days every month instaed of 10 days average. The total seasonal rain fall will certainly be about twice average.

Is there a relationship between GHG and the quick weather changes we're having?

Thomas Lankester

@richard schumacher

'if the temp goes up 4'C the ice sheets will slide into the sea, and sea level will go up 7 meters.'

That is just for the Greenland ice sheet. Western Antarctica would add another 7-8m ( If all the ice sheets go the rise is more than 60m.

Actually we do not need a 4C increase to get a significant sea level rise. Sea levels were 4-6m higher in the the last (Eemian / Ipswichian) interglacial when CO2/CH4 levels were lower than today. Recent GHG increases are still feeding through to temperature changes which in turn have not yet fed through to the ice sheets (classic lag effects).

The quaint US expression 'dead man walking' seems apt.


@MDF "why aren't we dead?"

My point was that changes like the one you quote fall into category (b) - we weren;t around to care. No-one from 11000-14000BC left any musings on the topic but I would be surprised if there was not a large amount of die off of human, plant and animal species in that time of fast change.

Just because a few people survived and went on to procreate does not mean I want myself or my family to experience the scenario of depletion and die-off first hand.


DC: we weren;t around to care.

What do you mean "we weren't around to care"? H. sapiens has been extent on this planet for at least 100,000 years

our direct ancestors for a lot longer than that.

"but I would be surprised if there was not a large amount of die off of human, plant and animal species in that time of fast change."

Given that arnold's theory says "90 something percent of living creatures over the next 100 or so years" are doomed, all you've done here is transform the question from "Why aren't we dead?" to "Where are the bodies?"

HarveyD: Is there a relationship between GHG and the quick weather changes we're having?

I've listened as professional meteorologists are asked this question.

Every single one, without exception to date, has refused to be drawn into the politico-scientifico charlie-foxtrot around global warming.

Instead, sensible pragmatists they are, they like to talk about the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO), and the other tangled mess of engines and pumps that create the climate.

Try this:

The PDO in particular is reported to be entering a cool phase. The last time this happened was from 1940-1980 or so. Here:

"From a societal impacts perspective, recognition of PDO is important because it shows that "normal" climate conditions can vary over time periods comparable to the length of a human's lifetime."

Interestingly, I am just old enough to remember (falsely?) the winters in southern Ontario in the late 1970's -- winters I have never seen since. But this has the anti-AGWer's all excited:

As far as I have been able to tell, no one has any idea at all about the physical underpinning of the PDO.


So when china and india stop building a new coal power plant every week, come talk to me about carbon caps and credits. untill then the CO2 levels will rise even if the whole western world stoped buring fossil fuels and trash our lifestyles. Come on seriousely our species can adapt to 4'c we Humans survied not just one but probably 5 iceages since our evolutionary tree diverged from the other walking apes 100K years ago.yes losing coastal cities will suck but its not like people just cant walk to outrun the rising water of a few INCHES a year.


The point of the original article is that we're not going to succeed on this issue. CO2 levels are already too high, and realistically they are going to continue to rise. We are going to see at least 3 to 4 degrees C, i.e. 5 to 7 degrees F, of warming this century. That is, unless crazy ideas like ocean seeding or stratospheric aerosols turn out to work. But if not, then yes, we or our descendants will in fact need to deal with many feet of sea level rise, abandoning coastal areas.

The bottom line is that we should get started on that today. Bangladesh is going to have to solve this problem on its own, but every country, every state, every city can start taking steps. A good first step is to increase taxes and flood insurance requirements on new construction in coastal zones, to prohibitive levels. Flooding and droughts are going to be more widespread, so we need to improve dams and manage aquifers more aggressively. Crop yields can potentially improve, but we need to breed varieties that can benefit from greater warmth and a longer growing season.

The list goes on and on, and again the point is not to push some quixotic attempt to bring about world peace and love and a universal agreement to stop polluting. That is not going to happen, because it is in no one's individual interest. But everyone who lives near a coast, or is thinking of moving there, needs to be aware that that land is going to be under water in a few generations, which means that resale value is not going to be so hot. Everyone in a flood plain or a drought prone area needs to be aware that they may be forced out of their home as a climate refugee. All these considerations are matters that people can affect directly and can have enormous and long term impacts on their lives. Driving a Prius makes no measurable difference in the world; moving away from the coast can save your children's lives. This is where we should focus.


"Come on seriousely our species can adapt to 4'c we Humans survied not just one but probably 5 iceages since our evolutionary tree diverged from the other walking apes 100K years ago.yes losing coastal cities will suck but its not like people just cant walk to outrun the rising water of a few INCHES a year."

the population now is 6 billion and will soon be 9 billion. you have increasing population and decreasing habitable (and cultivatable) land area. it's not a matter of outrunning the incoming sea, it's that a greater and greater proportion of world's population live in a coastal zone about 120 miles wide, where they are most at risk from rising sea levels. sure, over decades this trend can be reversed, but generally people do not do anything until the problem is right in their face, by which time it will be too late.


sorry if it took some time to get back.
If I use your figures, save me having to undertake research on this specific period.
I will try to downplay the specific question re 14,000 years ago, other than to point out that you as say - it occurred on the trailing edge of an interglacial cold period.
any extinction (the issue here) would have occurred during the original but much slower cooling.
This 3000 year period occurred in prehistory.
Also in the context of extinctions, that the period 14,000 - 11,000 years ago is not particularly relevant.
In fact the 100,000 year time frame is not an era of much evolution in the context of new species.
Hence the time frame you refer to slipped under te radar.
I was thinking in the more serious context of mass extinctions.

These periods are followed by periods of fast evolution and expansions of new species (or) epansion in the range of minor species.
H sapiens may have partially met this criteria.

I would ask you to consider also that (I do remember some of this) climate change can (apparently) occur with great speed. That is rather the more import issue than whether I can be fallible in my understanding (or general explanation) of how the whole thing works.
I'm sure no one does. Personally I claim no expertise , only a generalist's working understanding.

I'll reword to better answer your criticism.

Paleantologists try to explain mass extinctions by hypothesizing various scenarios which may be accepted (or not) for various periods of time by their peers.

One of the useful tools in trying to explain extinctions is to try to correlate extinction events whether that be climatic , catastrophe IE meteorite, volcanic, sea level and land bridges that may allow predator specie like man, dog, cat, rat or insect lets call that a quaranteen issue.

Climatic changes have been often seen as closely associated to specie extant or range.
I am very familiar with this in relation to flora.
Temperature , seasonal climatic variation, which may affect snowfall,rainfall, pollinating insects and a balance in animal populations which may either disperse , consume or devastate any of many critical aspects of the interconnected web will often lead to local extinctions or if the threatened specie has limited range , then total.

The specific mode of action may be revealed by careful methodical study and yes interpretation.
So a number of studies using different methodology may well lead to different interpretation.
A number of such interpretations may contradict, agree expand or confuse the issue.

Extinctions occur naturally at a base rate over very long time frames or may accelerate in times of rapid change.
Climate is a major influence on any ecosystem.
Climate is determined by major and secondary influences and heat retention is determined largely by the composition of atmosphere.
Greenhouse gases are described in common usage as CO2 equivalent. Further broken down to short medium and long term. <5year, 5 - 20/50 100 and other longer lasting gases.

The whole interaction can become very complicated depending on how detailed we try to describe the system.
This leads to new understanding and observation.
Science isnt about knowing every thing.
That is not reason to abandon learning.
Knowledge advances when the contradictions and 'better fits' to the evidence can be described.
' Science' describes the methodical approah based on theory and observation subject to peer review and open to criticism,
No one working in any area of "science" would have a problem with that.
We don't say "they got it wrong" all science is on a path of improvement and understanding.

I am not about to be be drawn on 'my theory' - It does't exist.

I'm not prothelatising any thing new but I know a J curve when I see one and what it means.

The one at the top of this page is consistent with worst case scenarios consistent with the technologist's world view.

Allow me to use my words. "Thats not 'theory', that's lower school math."


Back again, It just occurs to me what you mean by 'your theory.'
fair question.
Which you mean for me to explain.

"According to some commentators A complete reading of all the scientific reports state " 0.8 degrees describes a real (accumulated)increase of 2o in the medium case in the moderate feedback case.
2 3 and 4 degree C really means 8 o."

This refers to some observations by various commentators that climate change of 'X' o caries implied real temperature change 'X+'

This is a concept that that's suggests that the Stern report, Ippc, Other scientific govt and economist reports as we are accustomed to reading or hearing about describe the first effects of 'accelerated climate change'
The problem with this way of interpreting the real situation is that small amounts of warming starting at 0.8oc lead to feed backs this is what I mean by 'implied warming'
The previous posts are an accurate representation of these 'implied' warming.

An example would be when a certain temperature increase above baseline causes glacial melting. This temp gets reported, but when albedo decreases as a result of decreased ice cover causing another ? x o rise , this is implied . Not considered 'scientific and so not added to 'official figures.'

Of course when we look back at past climate records we see the combined effects in the interpretations.
So for govt's press and 'Science' purposes, such unmeasurable effects as bush fires, methane releases, ocean carbon sink collapse, ice shelf disintegration leading to decreased albedo, and even further decrease in albedo if a larger sea surface through any ' 75 meter rise ' were to eventuate, to name a few.
These are not scientific , cant be quantified or included in the science and so are the 'Implied temperature increases' that I was referring to.
Pretty tough yes?

My mistake - I just didn't get your question.
Hope this explains.
regards Arn

Paul F. Dietz

Given that arnold's theory says "90 something percent of living creatures over the next 100 or so years" are doomed,

Given than most living creatures have lifespans much less than 100 years, this is trivially correct.


Plainly the references are to extinctions expected from this rate of warming. That the effects are in worst case scenario likely to be well and truly in evidence by the end of the century.
Of course succesfull mitigation may alleviate this to some degree.
But I'm sure this is plain and clear despite the less than elegant writing.
Acting stupid can become habitual.

the planet is over populated anyways so let few billion or more die off it would be good for those in the developed world we wont have to compete with the 3rd world from resources. The US is a net food exporter stop the exports and feed americans we have vast land in the american southwest can we can move displaced americans too use nuclear power to desal salt water and green up the deserts, most the desert southwest is underlain by massive deep salt water aquifers pump it up and desalt it. nevada and nm are already thinking about doing this the amount of paleo salt water is so massive it will take hundreds of years to depleate the resources.

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