by Michael Mann, Stefan Rahmstorf, Gavin Schmidt, Eric Steig, and William Connolley
Senator James Inhofe (R) of Oklahoma recently provided us with an update of his views on the issue of climate change in a speech given on the opening senate session, January 4, 2005. His speech opened with the statement:
As I said on the Senate floor on July 28, 2003, “much of the debate over global warming is predicated on fear, rather than science.” I called the threat of catastrophic global warming the “greatest hoax ever perpetrated on the American people,” a statement that, to put it mildly, was not viewed kindly by environmental extremists and their elitist organizations.
Cutting through much of his polemic, Inhofe’s speech contains three lines of scientific argument which, according to him, provide “compelling new scientific evidence” that anthropogenic global warming is not threatening. We here submit his statements to scrutiny.
(1) The Paleoclimate Record
Inhofe relies upon novelist Michael Crichton (see here and here) to support his contention that
“We are also in the midst of a natural warming trend that began about 1850, as we emerged from a 400 year cold spell known as the Little Ice Age.”
Scientific studies come to the opposite result. All published scientific investigations of the causes of 20th century warming have consistently found that natural factors alone cannot explain the warming. Model simulations of large-scale temperature changes in past centuries , for one, can only reproduce the post-“Little Ice Age” warming through the inclusion of non-natural, anthropogenic forcing. The IPCC concluded in its 2nd asessment report that “that there is a discernible human influence on global climate”, based in fact on a variety of different techniques, including so-called “Detection and Attribution” studies. These studies involve detailed analyses of the spatial patterns of the observed 20th century changes, which differ for different causes of warming (e.g. anthropogenic factors such as increased greenhouse gases or industrial aerosols, or changes in land use, and natural factors such as changes in solar output or explosive volcanism), each of which have their own unique spatial pattern or “fingerprint”. Another simple reason that natural causes cannot explain recent warming is that none of the natural factors which could potentially cause warming (e.g., the combined solar+volcanic forcing or even the somewhat more dubious hypothesized forcing by cosmic ray flux changes) show a trend since the mid 20th century.
Inhofe then launches into a slew of criticisms of the “Hockey Stick” reconstruction of past temperature changes in this speech, touching on every one of our documented “myths”. Consider, for example, his reference to
“the well-known phenomena of the Medieval Warming [sic] Period–when, by the way, it was warmer than it is today”
All quantitative paleoclimate reconstructions of the past millennium published in the scientific literature have come to the opposite conclusion. They consistently find that late 20th century warmth is anomalous in the context of at least the last 1000 years for the Northern Hemisphere on the whole. Though certain regions appear to have exhibited mild conditions during the so-called “Medieval Warm Period”, there is no credible evidence we are aware of that average temperatures for the Northern Hemisphere or globe were as warm as (let alone warmer than) the late 20th century.
Inhofe then attempts to criticize the “Hockey Stick” reconstruction by citing a modeling study by the German GKSS group that actually supports the “Hockey Stick” conclusion that late 20th century warmth is anomalous in the context of the past 1000 years (see GKSS curve in Figure ) as well as the conclusion that this warmth can only be attributed to anthropogenic influences.
Furthermore, he attempts to criticize the methodology underlying the Mann et al (1998) reconstruction (one of more than a dozen estimates coming to essentially the same “Hockey Stick” conclusion), based on a reference to a comment by “three geophysicists from the University of Utah” [Chapman et al (2004)–see the response here] related to a modeling study by Mann and Schmidt (2003). That study has nothing to do with the Mann et al (1998) temperature reconstructions or methodology whatsoever (and did not even reference them) , but instead analyzed the factors governing the difference between ground surface temperature and land air temperature change in a climate model simulation of the latter 20th century.
(2) Global Sea level Rise
Estimates from tide gauges indicate that sea level has changed at the rate of 1.8 to 2.4 mm/yr over the last century. Satellite altimeter estimates currently show a global sea level change of 2.8+/- 0.4 mm/yr over the last 12 years. Due to the different methodologies involved, a direct comparison of the two values is not straightforward, but the satellite results provide absolutely no support for Inhofe’s contention that “there is a total absence of any recent acceleration in sea level rise”.
(3) Recent Arctic warming
Inhofe contends that “current Arctic temperature is no higher than temperatures in 1930s and 1940s” and cites many studies that appear to agree with him. However, the context for those studies is important and was well covered in the Arctic Climate Impact Assesment. In particular, natural variability in the climate system is particularly large in the high latitudes, such as the Arctic. This implies that temperatures from any one or two years may not be very representative of a long term trend. Arctic temperatures did indeed have a peak around 1940, but the decadal mean temperatures are now (1995-2004) warmer than the mean over 1935-1944. The variations in temperature in the Arctic resemble the global mean changes over the last century but are larger, clearly demonstrating the effect of polar amplification. More important are the causes of these temperature changes, and this cannot be determined simply by looking at one time series (this is further discussed here). The current consensus view is that warming in the 1940s was likely a combination of increasing GHG and solar forcing combined with a significant amount of internal variability, particularly associated with the North Atlantic. The subsequent cooling was related to the post-war increase in (mainly) sulphate aerosols. Subsequent to the 1970’s greenhouse gas forcing has become dominant, leading to the recent warming.
As is made very clear in the ACIA report, the Arctic is a complex and dynamic environment. It is well known that changes to atmospheric circulation associated with the North Atlantic Oscillation (NAO) can have important consequences for temperatures in the region. Over the last 35 years, the NAO has strengthened (implying more westerly winds), and this has lead to enhanced warming over Eurasia, and consequent cooling over southern Greenland, particularly in winter. Thus the Arctic is warming despite this dynamical trend, which itself may be related to anthropogenic forcing (Gillett et al, 2002).
Finally it is worth providing a bit of context for this latest speech. Inhofe has a history of making inflammatory and incorrect claims about the science of climate change. He previously gave a speech on the senate floor in July 2003 on “The Science of Climate Change” (partial transcript here) in which he stated that “catastrophic global warming is a hoax” and made a rather substantial number of false claims about the science. In fact, Senator John McCain (R) of Arizona subsequently provided two climate scientists mentioned specifically by Inhofe, Dr. Stephen Schneider of Stanford University (whom Inhofe referred to as “the father and promoter of the catastrophic global warming fearmongers”) and Dr. Tom Wigley of the National Center for Atmospheric Research, the opportunity to respond to several of these false assertions in the Senate record–see the account provided in the article “Earth Last” by science journalist Chris Mooney. In this speech, Inhofe repeated many of the standard contrarian arguments challenging the mainstream, consensus view of the climate research community that the activity of human beings now has had a discernable impact on global climate and that this warming is likely to continue as anthropogenic greenhouse gas concentrations continue to increase. Most of these arguments are debunked on the pages of RealClimate. Inhofe, for example, once again promoted each of the “myths” we have documented about the “Hockey Stick” reconstruction of past temperature changes, citing contrarian criticisms that have since been thoroughly discredited.
Re: “All published scientific investigations of the causes of 20th century warming have consistently found that natural factors alone cannot explain the warming.”
Do your really mean “ALL”.
Response: Yes. All studies that have looked at the spectrum of different forcings all find that anthropogenic factors must be included.
Is legitimate science driven by consensus or by demonstated predictability of forcast results against actual results?
Response: Actual predicitibility is of course key (and there are many good examples). That is why the consensus has developed.
If recent observed surface warming trends cannot be explained by “natural forces” does that imply that all previous warming trends similarly aso cannot be explained as “natural” (divine intervention, extra-terrestrial interference etc)?
Response: That’s logical nonsense.
Re: “Estimates from tide gauges indicate that sea level has changed at the rate of 1.8 to 2.4 mm/yr over the last century. Satellite altimeter estimates currently show a global sea level change of 2.8+/- 0.4 mm/yr over the last 12 years.”
Nils-Axel Morner, Paleogeophysics and Geodynamics, Stockholm University, S-10691, Stockholm, Sweden condludes in his studies of mean sea level:
“In the last 5000 years, global mean sea level has been dominated by the redistribution of water masses over the globe. In the last 300 years, sea level has been oscillation close to the present with peak rates in the period 1890-1930. Between 1930 and 1950, sea fell. The late 20th century lack any sign of acceleration. Satellite altimetry indicates virtually no changes in the last decade. Therefore, observationally based predictions of future sea level in the year 2100 will give a value of +10±10 cm (or +5±15 cm), by this discarding model outputs by IPCC as well as global loading models. This implies that there is no fear of any massive future flooding as claimed in most global warming scenarios.”
How do you account for the divergence of “facts” presented. Who am I to believe you or him? Does science require that I take a side and believe in one over another? When there is divergence of opinion how does science establish who should be believed?
Response: We are unaware of where Dr. Morner gets his data. If you go to the official website for the TOPEX/POSEIDEN JASON data http://sealevel.colorado.edu, all the data, methods and results are presented. See also
Cazenave and Nerem (2004) for a review.
[Additional response: the text you quote is from a conference abstract (1) not a scientific paper. The idea that altimetry shows no increase is simply nonsense. Read C+N – William]
“Inhofe repeated many of the standard contrarian arguments challenging the mainstream, consensus view of the climate research community….”
My understanding of science is that advances are always made by through the challenging of the “consensus view”. Is that wrong? Is science actually advanced through by the polling of selected opinion? Who selects who and who is not worthy of promulgating their an opinions? Is this done by editioral judgement or some other process? How would bias be eliminated from the process?
Response: You are in principle correct. However not every challenge is an advance. While some are, most of them end up being without merit. Please see our other posts on how the consensus on this issue has been formed. – gavin
So why don’t you take on Michael Crichton? He’s the guy who reaches a large segment of the reading public. If you don’t think a novelist is someone to take seriously, look at the effect Dan Brown’s The DaVinci Code is having on religous scholars. Or the “left behind” novels. People believe that stuff and you’re making a mistake if you don’t recognize their influence.
[Response: I think you overlooked the links we provided in “Inhofe relies upon novelist Michael Crichton (see here and here)…” to our previously posted criticisms of Crichton’s writings on “RealClimate”. -mike]
Chris Mooney’s post on Inhofe is worth reading too: here.
I disagree with Sen. Inhofe’s claim that the debate is predicated on fear. In fact, it seems the problem with global warming is that is it NOT so immediately scary to inspire people to get off their behinds to do something about it (or maybe stay on their behinds, rather than drive around polluting the place). At my age, I don’t have much personal fear about global warming. For me the strong motivating force and debating point is ethics and justice. I don’t feel right causing problems for poor people and future generations, even if those problems were to be quite mild, and even if they were not proven at the .05 significance level. It isn’t just that I benefit at their expense, but also that I am not benefitting at all from the inefficiency portion that is contributing to global warming. We pay higher prices for inefficiently produced goods.
People have been rightly focused on the recent tsunami, but there is a difference between being a victim of a natural disaster and being a victim at the hands of people who know they are harming you. Even though the effect may be the same for a person in terms of loss of life, property, livelihood, or bodily harm, there is often a greater sense of injustice in human-caused harm, perhaps leading to a societal demoralization and cynicism that people are just plain evil. Another way of looking at it is, we can do something to help reverse or reduce global warming and the possibility of runaway global warming, if it is not too late, whereas we really cannot stop earthquakes & volcanos, etc.
So, whether the projection be little harm or great harm, whether it is proven at the .05 level or .50 level, it is not fear, but a sense of ethics and justice that leads me and perhaps most other environmentalists to do what we can to reduce greenhouse gases, especially through means that save us money, or don’t cost us (which might cut our GH emissions by 3/4, given current technology). Victims tend to feel an even greater injustice, anger, and disgust when the perpetrator did it for nothing, but just out of ornery, arrogant meaness, and at expense to himself.
I’m always (slightly) amused by the arguments of Crichton, Inhofe, et al (plus various comments left behind here) that there is some inherent value to “challenging the orthodoxy” (cf. Crichton’s comment that he relies upon retired climate scientists over those currently practicing). They’re obvious unaware that, for most of the discipline’s life, anthropogenically-forced global warming was a distinctly contrarian view. It took a lot of reseach and modeling to debunk the notion that forcings would be regulated by homeostatic processes (oceanic CO2 uptake, &c.), and it wasn’t until the weight of the evidence was almost self-evident that climate scientists admitted that the contrarian view was correct.
So there *can* be value in challenging the orthodoxy. Greenhouse warming is evidence of that.
Very informative post. Thanks.
It is useful to focus on recent data results as well as the sources you cite. For example, RE: Arctic Warming, NAO, Global Sea Level Rise – there is a report of a new study forthcoming in Geophysical Research Papers by Bill Krabill and others here showing – I quote:
There are other such data studies that have appeared recently (e.g. this GEUS study regarding Greenland’s ice sheets). So despite some cooling of southern Greenland in winter (NAO), I think it is useful to cite these other data studies to point out how the worrying signals of on-going warming are piling up.
Isn’t there any legal action you can take when someone says something about your work that is false and damaging to your reputation?
[Response: Article I, Section 6 of the U.S. Constitution states “The Senators and Representatives … for any speech or debate in either House, they shall not be questioned in any other place.” This means (see e.g. this article) that whatever a Senator says about any citizen of the United States, he or she cannot be brought into a court of law, or sued for slander as long as it was said on the senate floor.]
Keep up the good work.
Hope you can find some time to watch these people, EdZ…
It is our duty to watch them. Thank you RC for watching them.
D
Senator Inhofe and novelist Michael Crichton need to see that climate warming
is happening in many regions of the world, including the Arctic.
1. “Using a suite of microwave remote sensing instruments aboard satellites,
scientists at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., and
the University of Montana, Missoula, have observed a recent trend of earlier
thawing across the northern high latitudes.”
http://www.nasa.gov/centers/goddard/news/topstory/2003/1210landfreeze.html
2. Earlier in the Year Snowmelt Runoff and Increasing Dewpoints for Rivers
in Minnesota, Wisconsin and North Dakota
http://www.mnforsustain.org/climate_snowmelt_dewpoints_minnesota_neuman.htm
This is the standard tactic that has been used by industry for many years (and now, unfortunately, by many in government). Whenever an environmental or health problem is discovered (phosphate eutrophication of lakes, atmospheric pollution and acidic deposition, ozone layer depletion, health and addictive effects of smoking, and now global warming impacts), these people repeat over and over false information and opinions of the small minority of scientists who support their views.
Inhofe seems to have it out for anyone who is concerned about environmental issues.
After the League of Conservation Voters endorsed John Kerry for President, Inhofe went on a witch-hunt and had a report created by the Senate Public Works Committee (which he chairs) that concluded:
“Today’s environmental groups are simply political machines reporting millions in contributions and expenditures each year for the purpose of raising more money to pursue their agenda. Especially in this election year, the American voter should see these groups and their many affiliate organizations as they are – the newest insidious conspiracy of political action committees and perhaps the newest multi-million dollar manipulation of federal election laws.”
Clearly Inhofe is working hard to paint people concerned about environmental issues to be “anti-American”.
Stephen (#10) —
“Whenever an environmental or health problem is discovered (phosphate eutrophication of lakes, atmospheric pollution and acidic deposition, ozone layer depletion, health and addictive effects of smoking, and now global warming impacts), these people repeat over and over false information and opinions of the small minority of scientists who support their views.”
Don’t worry, little Stevie! That’s just the All-Benevolent Free Market at work!
[Not that I object to market economics… I only decry the total, facile trust in the Invisible Hand that some people seem to have.]
Not to stir up the political pot too much, because this is a science blog, but I’m sad to say that the following point, made last spring by Chris Mooney, is well worth mentioning in the context of this discussion:
“If Inhofe is out of step with science, though, he’s right in line with his conservative and pro-business constituency. Since 1999, according to the Center for Responsive Politics, Inhofe has received almost $300,000 in campaign donations from oil and gas interests and nearly $180,000 from electric utilities. In the 2002 election cycle, he received more oil and gas contributions than any senator except Texas’ John Cornyn.”
Of all the professional climate researchers who Senator Inhofe cites in support of his characterization of global warming as “greatest hoax ever perpetrated on the American people … an article of religious faith”, I wonder how may would endorse that view.
Regarding the above article where you say
All published scientific investigations of the causes of 20th century warming have consistently found that natural factors alone cannot explain the warming
How much warming cannot be explained by natural factors, i.e. how much is thought to be probably due to the enhanced greenhouse effect.
[Response: An excellent answer to this question is provided by Dr. Thomas Crowley in the paper:
Crowley, T.J., Causes of Climate Change over the Past 1000 Years, Science, 289, 270-277, 2000.
Crowley (2000) forced an “Energy Balance” climate model with both (a) combined natural+anthropogenic forcing (this is one of the modeling results shown in our comparison here) and (b) natural (solar+volcanic) forcing only. Based on a comparison of the two, Crowley concludes that “The joint effects of solar variability and volcanism (Fig. 3B) indicate that the combination of these effects could have contributed 0.15° to 0.2°C to the temperature increase (Fig. 1) from about 1905-1955, but only about one-quarter to the total 20th-century warming.”. In other words, only a very small amount of the 20th century warming can be explained by natural forcing. The majority of the warming can only be explained by anthropogenic forcing. Other modeling studies support the same conclusion. -mike]
Re #15
thanks for the reply.
But I’m still not totally clear on this. Gavin – in response to previous questions – told me that
1. CO2 effects on climate had only occurred recntly, i.e. in recent decades.
[Response: Gavin did not say this at all. You need to read his comments again. -mike]
2. There is a lag in terms of CO2 effect of about 20 years – this being the reason that warming will continue even if CO2 levels remain the same.
[Response: The lag is not fixed, but depends on the timescale of the forcing. Nonetheless, there is a lag on the order of decades to a century (depending on the component of the climate system one is talking about–e.g. upper ocean temperature vs. deep ocean temperature, glacial ice volume, sea level) in the response of the climate to anthropogenic forcing. This lag is of course implicit in the climate models discussed above. -mike]
I was under the impression that pre-1900 CO2 levels were determined to be around 280 ppm (i.e. virtually pre-industrial levels) which suggests that the warming in the early part of the 20th century (1910-45) was not due to increased CO2.
[Response: You correctly cite the approximate ‘pre-anthropogenic’ concentration of 280 ppm, but this applies to pre-19th century values, not the values at the beginning of the 20th century. CO2 concentrations have been increasingly steadily since 1800. By the turn of the 20th century, CO2 levels had already risen to about 295 ppm. This represents a radiatively significant increase–the model simulations referred to indeed exhibit some 19th century warming in response to this increase, though many of the modeling studies include other factors that lead to negative radiative forcing trends during the late 19th century (e.g. human land-use changes) which offset any 19th century warming due to CO2 increases. -mike]
Coming from a country, as I do, that has ratified the Kyoto accord -could you explain the gist of the accord and how it will assist in reducing global warming, if at all?
And a second question -how far can global warming go? I mean we can’t exactly drive CO2 levels to 100% can we?
[Response: CO2 concentrations are measured in terms of their “parts per million (ppm)” in the atmosphere. Right now, concentrations are close to 370 ppm. Under the so-called “business as usual” scenario, where no actions are taken to curtail fossil fuel burning, concentrations will likely reach double their pre-industrial values (280 ppm), i.e, approximately 550 ppm, sometime mid 21st century. That’s less than one part CO2 for every 1000 parts atmosphere, still a very small fraction of the atmosphere. However, because CO2 has a substantial radiative influence on the atmosphere due to its Infrared absorptive properties (what makes it a “greenhouse” gas), even this seemingly modest increase in the concentration of CO2 in the atmosphere would lead to several degrees C of estimated warming of the earth’s surface. -mike]
Finally, a third, if I may… is the hockey stick model really a kind of logarithmic chart? and if so, when would temperatures begin to increase substantially in extremely short periods of say a year or so?
[Response: No, the various charts shown on the pages of “RealClimate” of global or hemispheric temperature changes (either reconstructed from proxy data, calculated from modern instrumental records, or estimated from model simulations) are shown in the proper relative units of degrees (C). No logarithmic or other transformations are taken. -mike ]
Your work is good reading. Thank you
[Response: Thanks–we’re glad you find it useful. -mike]
Following up on #16 and #17, could someone discuss the timing of reductions in GHG emissions that are required to stabilize GHG concentrations in the atmosphere at a level that minimizes climate change impacts? I’ve looked at some of the IPCC graphs in the Summary for Policymakers, which appear to suggest that emissions have to begin decreasing almost immediately and reach rates below 1990 rates within a few decades in order to stablize GHG levels in the atmosphere in the 500 ppm range which would keep temperature increases at a couple of degrees C as I understand it. I’m asking in order to better understand the urgency of making GHG emission reductions. In other words, do we have time to debate this problem some more before making the hard choices involved in reducing emissions; what are the consequences of delaying action? Do we have 10 years, 100 years? Thank you for providing this blog; it’s very informative.
Just wanted to say that this is a great blog and it is filling a very important need. Keep up the good work! Ana
[Response: Thanks for your support. -mike]
FYI
Forwarded message from:
http://finance.groups.yahoo.com/group/fuelcell-energy/
Huge CO2 emission cuts proposed
Yomiuri Shimbun
The government is to propose a massive reduction in carbon dioxide
emissions in advanced nations to levels one-fourth of those in 2002 by
2050, government sources said Tuesday.
The proposal will be made in the government’s long-term energy policy
outlines to be compiled later this year. The government has set 2050
and 2100 as target years for reductions in emissions, to arrest global
warming and deal with the depletion of oil and other fossil fuels .
In order to control global warming, the government will propose a
reduction by 2050 of CO2 emissions in advanced nations to 3.1 billion
tons, one-fourth of 2002 levels, and by 2100 to 600 million tons,
one-twentieth of 2002 levels.
According to the sources, the government is to announce interim policy
outlines soon and to finalize them in August. The outlines split
energy consumption into four areas: industry, household and other
civil use, transportation, and electrical power. According to the
yet-to-be-published outlines, within the categories, oil consumption
in all areas except for transportation will be almost zero by 2050. By
2100, although natural gas will remain as an energy source for
industry and transport, most energy consumption will be met by
renewable energy sources such as nuclear power, hydrogen energy and
solar energy.
To achieve these goals, the government proposes that the nation engage
in research and development of new technologies in three
areas–nuclear power, including establishing reprocessing of nuclear
fuel and total control over the nuclear fuel cycle; carbon
sequestration technology to place CO2 underground, and developing
renewable energy sources such as hydrogen or solar power as well as
energy-saving technology.
The nuclear fuel cycle refers to reprocessing of spent nuclear fuel so
it can be reused and made less hazardous. Spent nuclear fuel has been
shipped to Europe for reprocessing or stored around the country. The
government hopes that current technological developments can be
extended in the future and these will have the potential to provide
energy that can overcome environmental problems and depleting energy
resources.
However, the outlines point out that developing other new
technologies, such as hydrogen power, should be promoted
simultaneously, since public acceptance of full-scale nuclear power
operations is uncertain due to safety concerns, such as the handling
of radioactive waste.
http://www.yomiuri.co.jp/newse/20050112wo01.htm
j2997
— End forwarded message —
Tsunami can not be related to the recent rise of sea level due to the global warming. Is this correct? If so, why are they denyinng the small increase of the sea level in Smatra?
[Response: the tsunami was caused entirely by an earthquake. It has nothing to do with long term sea level rise – William]
Having discovered your blog through several days of worried surfing following the recent UK documentary programme ‘Horizon’ on the suppressant effect of ‘Global Dimming’ on GHG-induced temperature rise and the urgent requirement to revise GW effect estimates upwards, I have to say that it is an excellent and informative resource, though not a source of comfort. Given that major corporates and governments respond to voter and consumer pressure only with reluctance and will usually fight to maintain the status quo, that leaves us with civil society; an underestimated power in the most-polluting nations. Civil society is made up of consumers/voters/employees/managers and local administrations. I am keen to promote practical steps to inform and encourage, rather than simply scare or berate community groups and NGO’s into including CO2 emission reduction in virtually all policy and procurement decisions. We are seeing success in the UK with long-overdue improvements to recylcing. The conventional wisdom has been/is still amongst local authority officers/waste mgmt. companies that 23-24% civersion from landfill is the best we can do, but we already have some social enterprises targeting 70% + diversion within 3 years of our funding programmes. Householders have largely said “give us the services and we will use them”. The same is true of organic food and good public transport etc. What practical steps can we undertake, in addition to strategies to reduce energy use in buildings, tranpsort & the home, to promote C02 capture through agriculture/forrestry etc? We have the ability to inform and support community management of woodlands and green spaces in both urban and rural areas and with the restructuring of production subsidies to farmers, more opportunities for non-food crops such as bio-fuel, coppice and woodland planting will emerge. How much planting, and of what species would we need to do to reinforce the emissions reduction with Carbon capture? Where can I get more info on this.
thanks for your help
Colin Keyse: grant manager environment WCVA
Can someone follow up on #18 re: timing of GHG reductions? Like many others, I hate to be merely a scaremonger, but it’s difficult to imagine that real reductions in GHG’s are likely to start any time soon – and if they did, the best we might achieve is at least a 2 degree C temperature rise. How do we avoid instilling a feeling of hopelessness, particularly in young people (like the ones I teach)?
Great blog – keep up the good work.
I’m not a climate scientist however, I wonder about a comment I read that stated that the the 20th century has been shown to be the warmest in the last 1000 years.
And yet isn’t there much evidence of viking settlements on Greenland where apparently they lived for long periods with significant cultivation/agriculture which of course could not be contemplated in today’s Greenland.
Can anyone explain this anomoly?
[Response: The first comment is about the global mean temperature, i.e. a region far greater than Greenland, whereas the latter is believed to have had a more regional character. rasmus-]
[Response: Even still, there is as much “myth” as “fact” here. It is certainly not the case that the locations settled by the Vikings in early centuries could not be settled today. The climate in the southern Fjords region of Greenland has been relatively hospitable for quite some time. However, climate was probably not the most important factor controlling the pattern of Viking settlement. From Jones and Mann (2004) [Jones, P.D., Mann, M.E., Climate Over Past Millennia, , Reviews of Geophysics, 42, RG2002, doi: 10.1029/2003RG000143, 2004]:
Iceland was settled mainly from Norway and the northern British Isles beginning A.D. 871. The further migration to SW Greenland approximately one centurylater, by a small group of Icelanders, was the result primarily of a political and economic need to leave Iceland [Ogilvie and Jo´nsson, 2001]. Climate was not a factor in their decision despite claims otherwise that still appear in the literature [Soon and Baliunas, 2003; Soon et al., 2003]. The SW Greenland settlements survived for many centuries, but in the mid-14th century the more marginal and more northerly located Western Settlement was abandoned. There were a number of reasons for this, including culture and economic factors. However, it seems likely that climate did play a part in the abandonment. The focus of their economy on animal husbandry denied them the advantages of hunting marine and other mammals that ensured the survival of their Inuit neighbors. A series of unusually late springs and cold summers, for example, may have helped to make a marginal situation untenable [Barlow et al., 1997]. The more southerly Eastern Settlement survived to around the mid-15th century [Buckland et al., 1996]. -mike]
[Response: Jared Diamond’s new book “Collapse” also has a lot about this case. He too thinks the climate connection is overstated (see an interview here) – gavin]