Climate & Climate Change

It has become common practice in climate science for a press release reporting the findings of a new paper to precede the publication in the journal concerned. Thus, the Lockwood and Frohlich paper ‘Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature’ (M. Lockwood and C. Fröhlich Proc. R. Soc. A doi:10.1098/rspa.2007.1880; 2007, 10th July) was announced in the 5th July edition of the journal Nature under the headline ‘No solar hiding place for greenhouse sceptics.’

It came as no surprise that Real Climate’s Stephan Rahmstorf was first out of the woodwork:

“This paper is the final nail in the coffin for people who would like to make the Sun responsible for present global warming,” says Stefan Rahmstorf, a climate scientist at the Potsdam Institute for Climate Impact Research in Germany.

Normally papers are published because there is new research to report, but not this time it seems:

Mike Lockwood, says he was “galvanized” to carry out the comprehensive study by misleading media reports. He cites ‘The Great Global Warming Swindle’, a television programme shown in March by Britain’s Channel 4, as a prime example.

But wait! There’s more:

Ken Carslaw, an atmospheric scientist at the University of Leeds, UK, points out that solar effects might still be possible. They might have acted to cool the climate in recent decades, but been overwhelmed. If so, the climate could be more sensitive to greenhouse gases than is generally thought, and future temperature increases might be greater than expected if a countervailing solar effect comes to an end.

Lockwood was “galvanised” again in response to criticism of his paper in the UK’s Daily Telegraph:

“I am one of the authors of the Royal Society global warming paper that you say is simple and fundamentally flawed (Comment, July 15). Simple? The idea was to present a straightforward demonstration, without recourse to complex climate models. Flawed? None of the three academic referees the paper was subjected to found any flaws.

Climate change is by far the greatest threat to everyone’s standard of living. Unlike political parties, companies, media stars, works of art, consumer products and even social trends and national economies, a scientific reality is immune to spin.”

(Prof) Mike Lockwood, Southampton University

Meanwhile, Piers Corbyn of Weather Action, who appeared in The Great Global Warming Swindle, had a letter published in The Guardian:

In desperate attempts to shore up their crumbling doctrine of man-made climate change, Professor Lockwood and Henry Davenport (Letters, July 14) themselves cherry-pick data. Prof Lockwood’s “refutation” of the decisive role of solar activity in driving climate is as valid as claiming a particular year was not warm by simply looking at the winter half of data. The most significant and persistent cycle of variation in the world’s temperature follows the 22-year magnetic cycle of the sun’s activity. So what does he do? He “finds” that for an 11-year stretch around 1987 to 1998 world temperatures rose, while there was a fall in his preferred measures of solar activity. A 22-year cycle and an 11-year cycle will of necessity move in opposite directions half the time.

The problem for global warmers is that there is no evidence that changing CO2 is a net driver for world climate. Feedback processes negate its potential warming effects. Their theory has no power to predict. It is faith, not science. I challenge them to issue a forecast to compete with our severe weather warnings – made months ago – for this month and August which are based on predictions of solar-particle and magnetic effects that there will be periods of major thunderstorms, hail and further flooding in Britain, most notably July 22-26, August 5-9 and August 18-23. These periods will be associated with new activity on the sun and tropical storms. We also forecast that British and world temperatures will continue to decline this year and in 2008. What do the global warmers forecast?

Piers Corbyn
Weather Action

The BBC’s verdict was ‘No Sun link’ to climate change.

In Part 2 I’ll take a closer look at some of what the L& F paper did, and didn’t say.

Ilulissat, Greenland – The July 27-29 2007 U.S. Senate trip to Greenland to investigate fears of a glacier meltdown revealed an Arctic land where current climatic conditions are neither alarming nor linked to a rise in man-made carbon dioxide emissions, according to many of the latest peer-reviewed scientific findings. Recent research has found that Greenland has been warming since the 1880’s, but since 1955, temperature averages at Greenland stations have been colder than the period between 1881-1955.

A recent study concluded Greenland was as warm or warmer in the 1930’s and 40’s and the rate of warming from 1920-1930 was about 50% higher than the warming from 1995-2005. One 2005 study found Greenland gaining ice in the interior higher elevations and thinning ice at the lower elevations. In addition, the often media promoted fears of Greenland’s ice completely melting and a subsequent catastrophic sea level rise are directly at odds with the latest scientific studies. These studies suggest that the biggest perceived threat to Greenland’s glaciers may be contained in unproven computer models predicting a future catastrophic melt.

As a representative of Environment & Public Works Committee Ranking Member, Senator James Inhofe (R-Okla.), I made the trek to the Arctic Circle with the Senate delegation to the land the Vikings once farmed during the Medieval Warm Period.

Senators and their staff viewed majestic giant glaciers and icebergs in the Kangia Ice Fjord and in Disko Bay via helicopter, boat and on foot, during the three day 24 hours of daylight trip which began in the Arctic city of Kangerlussuaq, Greenland.

In an informational handout, participants of the Senate trip to Greenland were shown a depiction of coastal flooding that illustrated what would happen if most of the ice on Greenland was to melt and sea levels rose nearly 20 feet. The handout on Greenland was written by UN scientist Dr. Richard B. Alley, who is also a professor of Geosciences at Penn State University and traveled with the Senate delegation. Dr. Alley noted that the illustration of coastal flooding was not a forecast or a prediction, but merely an illustration of what could happen.

Dr. Alley’s handout stated in part, “We don’t think Greenland could melt completely in less than many centuries, but it might get warm enough this century to start complete melting.”

During the trip, a Danish scientist and Danish government officials appealed to the U.S. government to act now to address global warming and used the prospect of Greenland melt fears as a wake up call for such action. But the very latest research reveals massive Greenland melt fears are not sustainable. According to a survey of some of the latest peer-reviewed scientific reports, current Greenland temperatures are neither alarming nor linked to a rise in man-made carbon dioxide emissions.

Sampling of Recent Scientific Studies:

1) A 2006 study by Danish researchers from Aarhus University found that “Greenland’s glaciers have been shrinking for the past century, suggesting that the ice melt is not a recent phenomenon caused by global warming.” Glaciologist Jacob Clement Yde explained that the study was “the most comprehensive ever conducted on the movements of Greenland’s glaciers, according to an August 21, 2006 article in Agence France-Presse. “Seventy percent of the glaciers have been shrinking regularly since the end of the 1880’s,” Yde explained. [EPW Blog note: 80% of man-made CO2 emissions occurred after 1940. Niels Tvis Knudsen of Aarhus University co-authored the paper.

2) A 2006 study by a team of scientists led by Petr Chylek of Los Alamos National Laboratory, Space and Remote Sensing Sciences found the rate of warming in 1920-1930 was about 50% higher than that in 1995-2005, suggesting carbon dioxide ‘could not be the cause’ of warming.

“We find that the current Greenland warming is not unprecedented in recent Greenland history. Temperature increases in the two warming periods (1920-1930 and 1995-2005) are of similar magnitude, however the rate of warming in 1920-1930 was about 50% higher than that in 1995-2005,” the abstract of the study read.

The peer-reviewed study, which was published in the June 13, 2006 Geophysical Research Letters, found that after a warm 2003 on the southeastern coast of Greenland, “the years 2004 and 2005 were closer to normal being well below temperatures reached in the 1930’s and 1940’s.” The study further continued, “Almost all post-1955 temperature averages at Greenland stations are lower (colder climate) than the (1881-1955) temperature average.”

In addition, the Chylek led study explained, “Although there has been a considerable temperature increase during the last decade (1995 to 2005) a similar increase and at a faster rate occurred during the early part of the 20th century (1920 to 1930) when carbon dioxide or other greenhouse gases could not be a cause. The Greenland warming of 1920-1930 demonstrates that a high concentration of carbon dioxide and other greenhouse gases is not a necessary condition for a period of warming to arise. The observed 1995-2005 temperature increase seems to be within natural variability of Greenland climate. A general increase in solar activity [Scafetta and West, 2006] since 1990’s can be a contributing factor as well as the sea surface temperature changes of tropical ocean [Hoerling et al., 2001].”

“To summarize, we find no direct evidence to support the claims that the Greenland ice sheet is melting due to increased temperature caused by increased atmospheric concentration of carbon dioxide.” The co-authors of the study were M.K. Dubey of Los Alamos National Laboratory and G. Lesins, Dalhousie University in Canada.

3) An October 2005 study in the journal Science found Greenland’s higher elevation interior ice sheet growing while lower elevations ice is thinning. According to a November 8, 2005 article in European Research, “An international team of climatologists and oceanographers, led by the Nansen Environmental and Remote Sensing Center (NERSC) in Norway, estimates that Greenland’s interior ice sheet has grown, on average, 6cm per year in areas above 1 500m between 1992 and 2003.” Lead author, Ola M. Johannessen of NERSC “says the sheet growth is due to increased snowfall brought about by variability in regional atmospheric circulation, or the so-called North Atlantic Oscillation (NAO),” according to the article.

4) A February 8, 2007 peer-reviewed paper published in Science found two of Greenland’s largest glaciers have “suddenly slowed, bringing the rate of melting last year down to near the previous rate,” according to the New York Times blog (2-8-07). The report found that the Kangerdlugssuaq glacier’s “average thinning over the glacier during the summer of 2006 declined to near zero, with some apparent thickening in areas on the main trunk.” University of Washington’s Applied Physics Laboratory researcher Ian Howat, the lead author of the report, explained “Greenland was about as warm or warmer in the 1930’s and 40’s, and many of the glaciers were smaller than they are now.” “However, it does suggest that large variations in ice sheet dynamics can occur from natural climate variability,” Howat, also a researcher with the University of Colorado’s National Snow and Ice Data Center, explained. “Special care must be taken in how these and other mass-loss estimates are evaluated, particularly when extrapolating into the future because short-term spikes could yield erroneous long term trends,” Howat cautioned.

5) A July 6, 2007 study published in the journal Science about Greenland by an international team of scientists found DNA “evidence that suggests the frozen shield covering the immense island survived the Earth’s last period of global warming,” according to a Boston Globe article. (6-6-07) According to the article, the study indicates “Greenland’s ice may be less susceptible to the massive meltdown predicted by computer models of climate change, the main author (Eske Willerslev, professor of evolutionary biology at University of Copenhagen) said in an interview. “This may have implications for how the ice sheets respond to global warming. They may withstand rising temperatures,” Willerslev said. The article explained, “The discovery of organic matter in ice dating from half –a-million years ago offers evidence that the Greenland ice sheet remained frozen even during the Earth’s last ‘interglacial period’ – some 120,000 years ago – when average temperatures were 9 degrees Fahrenheit warmer than they are now.” Willerslev addressed scary computer model predictions of a massive Greenland melt. “[The study] suggests a problem with [computer] models” that predict melting ice from Greenland could drown cities and destroy civilizations, Willerslev said. The study found “Greenland really was green, before Ice Age glaciers enshrouded vast swaths of the Northern Hemisphere…somewhere between 450,000 and 800,000 years ago,” according to the article.

6) Climatologist Dr. Patrick Michaels of University of Virginia and the Virginia State climatologist wrote the scenario promoted by former Vice President Al Gore and others showing Greenland’s ice melting and raising sea levels by 20 feet is not supported anywhere in scientific literature, not even by the United Nations. “Where is the support for this claim? Certainly not in the recent [Intergovernmental Panel on Climate Change (IPCC)] Policymakers Summary from the United Nations. Under the [IPCC’s] medium-range emission scenario for greenhouse gases, a rise in sea level of between 8 and 17 inches is predicted by 2100. Gore’s film exaggerates the rise by about 2,000 percent,” Michaels wrote in a February 23, 2007 article. “According to satellite data published in [the journal] Science in November 2005,” Michaels wrote, “Greenland was shedding ice at 0.4 percent per century.” “Nowhere in the traditionally [peer-reviewed] refereed scientific literature do we find any support for Gore’s [Greenland melt] hypothesis,” Michaels concluded.

7) Geologist Morten Hald, an Arctic expert at of the University of Tromso in Norway has also questioned the reliability of computer models predicting a melting Arctic. “The main problem is that these models are often based on relatively new climate data. The thermometer has only been in existence for 150 years and information on temperature which is 150 years old does not capture the large natural changes,” Hald, who is participating with a Norwegian national team in Arctic climate research, said in a May 18, 2007 article. The article continued, “Professor Hald believes the models which are utilized to make prognoses about the future climate changes consider paleoclimate only to a minor degree.” “Studies of warm periods in the past, like during the Stone Ages can provide valuable knowledge to understand and tackle the warmer climate in the future,” Hald explained.

8) Polar expert Ivan Frolov, the head of Russia’s Science and Research Institute of Arctic and Antarctic Regions, said atmospheric temperature would have to much higher to make continental glaciers melt. “Many hundred years or 20-30 degree temperature rise would have made glaciers melt,” Frolov said in a December 14, 2006 Russian news article. Frolov noted that currently Greenland’s and Antarctic glaciers have the tendency to grow. The article explained, “Frolov says cooling and warming periods are common for our planet – temperature fluctuations amounted to 10-12 degrees. However, such fluctuations haven’t caused glaciers to melt. Thus, we shouldn’t be afraid they melt today.”

9) Physicist Dr. Syun-Ichi Akasofu, the former director of both University of Alaska Fairbanks’ Geophysical Institute and International Arctic Research Center who has twice been named “1000 Most Cited Scientists” told a Congressional hearing in 2006 that highly publicized climate models showing a disappearing Arctic were nothing more than “science fiction.” “All the papers since (the advent of satellites) show warming. That’s what I call ‘instant climatology.’ I’m trying to tell young scientists, ‘You can’t study climatology unless you look at a much longer time period.’”

10) In addition, current climate fears tends to ignore the fact that the Vikings arrived in Greenland around 1000 A.D. and found it to be habitable settlement that they farmed for hundreds of years. A 2003 Harvard University study found the Earth was warmer than today during the Medieval Warm Period from about 800 to 1300 A.D. without modern SUV’s or man-made CO2 emissions. The Vikings abandoned Greenland when the Little Ice Age took hold.

11) Another problem for predictions of catastrophic sea level rise due to polar ice melt is Antarctica is not cooperating with the man-made catastrophic global warming models. “A new report on climate over the world’s southernmost continent shows that temperatures during the late 20th century did not climb as had been predicted by many global climate models,” reads the February 15, 2007 press release announcing the findings of David Bromwich, professor of professor of atmospheric sciences in the Department of Geography, and researcher with the Byrd Polar Research Center at Ohio State University.

“It’s hard to see a global warming signal from the mainland of Antarctica right now,” Bromwich explained. The release explains that Bromwich’s research team found “no increase in precipitation over Antarctica in the last 50 years. Most models predict that both precipitation and temperature will increase over Antarctica with a warming of the planet.”

Top UN Scientist Explains Why Climate Models Predictions Are Failing

Recently, a top UN scientist publicly conceded that climate computer model predictions are not so reliable after all. Dr. Jim Renwick, a lead author of the IPCC 4th Assessment Report, admitted to the New Zealand Herald in June 2007, “Half of the variability in the climate system is not predictable, so we don’t expect to do terrifically well.”

A leading scientific skeptic of global warming fears, Dr. Hendrik Tennekes, former CEO of the Netherlands’ Royal National Meteorological Institute, took the critique of climate models that predict future doom a step further. Tennekes wrote on February 28, 2007, “I am of the opinion that most scientists engaged in the design, development, and tuning of climate modes are in fact software engineers. They are unlicensed, hence unqualified to sell their products to society.”

Ivy League geologist Dr. Robert Giegengack of the University of Pennsylvania noted “for most of Earth’s history, the globe has been warmer than it has been for the last 200 years. It has rarely been cooler,” Giegengack said according to a February 2007 article in Philadelphia Magazine. The article continued, “[Giegengack] says carbon dioxide doesn’t control global temperature, and certainly not in a direct linear way.”

Climatologist Dr. Timothy Ball explained that one of the reasons climate models fail is because they overestimate the warming effect of CO2 in the atmosphere. Ball described how CO2 stabilizes in the atmosphere and its warming impact diminishes. “Even if CO2 concentration doubles or triples, the effect on temperature would be minimal. The relationship between temperature and CO2 is like painting a window black to block sunlight. The first coat blocks most of the light. Second and third coats reduce very little more. Current CO2 levels are like the first coat of black paint,” Ball explained in a June 6, 2007 article in Canada Free Press.

New data is revealing what may perhaps be the ultimate inconvenient truth for climate doomsayers:

Global warming stopped in 1998.

Dr. Nigel Calder, co-author with physicist Henrik Svensmark of the 2007 book “The Chilling Stars: A New Theory on Climate Change,” explained in July 2007:

“In reality, global temperatures have stopped rising. Data for both the surface and the lower air show no warming since 1999. That makes no sense by the hypothesis of global warming driven mainly by CO2, because the amount of CO2 in the air has gone on increasing. But the fact that the Sun is beginning to neglect its climatic duty – of battling away the cosmic rays that come from ‘the chilling stars’ – fits beautifully with this apparent end of global warming.”

Perhaps the conversion of many former scientists from believers in man-made global warming to skeptics (LINK) and the new peer-reviewed research is why so many proponents of a climatic doom have resorted to threats and intimidation in attempting to silence skeptics. (See: EPA to Probe E-mail Threatening to ‘Destroy’ Career of Climate Skeptic – LINK )

One final note: To many residents of Greenland, a little warming may not be that bad. A June 7, 2007 Washington Post article detailed how Greenland’s residents were “cheering’ on warming. “I can keep the sheep out two weeks longer to feed in hills in the autumn. And I can grow more hay. The sheep get fatter,” said one resident.

from Marc Morano in Greenland

This is a cross post from the US Senate Committee on Environment and Public Works Inhofe Press blog. Links to the various recent scientific studies can be found at the original post by Marc Morano entitled ‘Latest Scientific Studies Refute Fears of Greenland Melt’: http://epw.senate.gov/public/index.cfm?FuseAction=Minority.Blogs&ContentRecord_id=175b568a-802a-23ad-4c69-9bdd978fb3cd&Issue_id

The Intergovernmental Panel on Cllimate Change (IPCC) estimates pre-industrial levels of CO2 based largely on information derived from ice cores. These are kilometres long cylinders of ice drilled (in short sections) from the Greenland and Antarctic icecaps.

The theory is that air bubbles trapped in the ice are samples of the ancient atmosphere, and thus give an accurate reading of CO2 levels in those ancient times. The ice cores tell us that the pre-industrial level of
CO2 was about 290 parts per million (ppm).

Of course it’s not that simple. There are many factors to take into account, because ice from deep down in the ice cap is under enormous pressure, and that pressure is released when the cores are brought to the surface.

A brief summary of some of the processes going on in ancient, deep ice can be found here:

http://geoweb.princeton.edu/people/bender/lab/research_ice_cores.html

Zbigniew Jaworowski, a multidisciplinary scientist, has long been a critic of the ice core CO2 record:

http://www.21stcenturysciencetech.com/2006_articles/IceCoreSprg97.pdf

http://www.larouchepub.com/eiw/public/2007/2007_10-19/2007-11/pdf/38_711_science.pdf

He makes a number of claims:

1. Ice core results reported before about 1985 showed higher CO2 levels than those reported since 1985, which he details in his 1997 paper.

2. Low pre-industrial concentration of CO2 in ice cores is an artefact caused by more than 20 physical-chemical processes. For example, CO2 is more than seventy times as soluble in water as is nitrogen, and liquid water is present in deep ice, even at -73C.

3. Drilling and retrieval of ice cores, including their decompression as they are brought to the surface, drastically disturbs the sample.

4. Subsurface melting of snow due to absorption of solar radiation is common in very cold sites, and may occur several times a year. This implies that the practice of dating ice cores using isotopes of oxygen, which assumes the temperature peaks are yearly events, is wrong.

The net result of these effects is to lower the CO2 levels in ice compared to that found in the atmosphere, by 30 – 50%, and to minimise fluctuations in CO2 in ice compared to the atmosphere.

Jaworowski illustrates this by comparing ice core data to other CO2 proxy data, such as stomata indices, which gives higher atmospheric CO2, with more variation than the ice core data over the last 8,000 years.

There is no doubt that ice core analysis is a highly technical subject, and scientists must make many assumptions when interpreting the data. One assumption that I personally found very interesting was that air inclusions in the snow and firn, or compacted granular snow, are well mixed with the atmosphere. In other words, the air in the hard packed snow is basically the same as the atmospheric air, down to the level of the ice. This could be 50 – 120 metres below the surface. Imagine hard packed snow that far down having a connection (and circulation with) the surface air. To me this is very counter-intuitive, but apparently Argon dating confirms it.

Jaworowski claims this is wrong, and that impenetrable layers, caused by melting and refreezing, cut off air inclusions from the atmosphere much earlier. This is the basis of his criticism that ice core data from the Siple core showed similar CO2 levels as the atmosphere did 83 years later, and thus the air in the ice core was assumed to be 83 years younger than the ice it was in.

Jaworowski has been criticised here:

http://www.someareboojums.org/blog/?p=7

The late Hans Oeschger, a prominent ice core scientist, was also critical of Jaworowski, and wrote a letter in 1995 expressing his views :

http://www.someareboojums.org/blog/?p=12

Following are some other links.

Jaworowski interview in May this year:

http://www.canada.com/nationalpost/news/story.html?id=25526754-e53a-4
899-84af-5d9089a5dcb6&p=1

Diffusion of CO2 in atmospheric gas analysis (on pp10 – 11)

http://www.biomind.de/nogreenhouse/daten/AIGnewsNov06.pdf

———————————

From Paul Williams who lives in the Adelaide Hills, Australia

Other contributions to this blog from Paul Williams include:

Hockey sticks and ancient pine tree, at https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/archives/001546.html
Measuring Atmosheric C02, at https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/archives/001983.html
Build Dykes to Beat Global Warming, at https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/archives/001983.html

Check it out. It could be an interesting discussion piece.

Helen

“Dirty snow may warm Arctic as much as greenhouse gases”

Helen is referring to Black Carbon, covered by Pielke Sr recently:

A New Paper That Highlights the First-Order Radiative Forcing Of Black Carbon Deposition

Having seen Ian Mott’s note on land change, I though I would post this paper suggesting that climate models and therefore the IPCC underestimate the effects of land use change on climate:

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D09117, doi:10.1029/2006JD007505, 2007

Observational estimates of radiative forcing due to land use change in southwest Australia

Abstract

Radiative forcing associated with land use change is largely derived from global circulation models (GCM), and the accuracy of these estimates depends on the robustness of the vegetation characterization used in the GCMs. In this study, we use observations from the Clouds and Earth’s Radiant Energy System (CERES) instrument on board the Terra satellite to report top-of-the-atmosphere (TOA) radiative forcing values associated with clearing of native vegetation for agricultural purposes in southwest Australia. Over agricultural areas, observations show consistently higher shortwave fluxes at the TOA compared to native vegetation, especially during the time period between harvest and planting. Estimates using CERES observations show that over a specific area originally covered by native vegetation, replacement of half the area by croplands results in a diurnally averaged shortwave radiative forcing of approximately −7 W m−2. GCM-derived estimates for areas with 30% or more croplands range from −1 to −2 W m−2 compared to observational estimate of −4.2 W m−2, thus significantly underestimating radiative forcing due to land use change by a factor of 2 or more. Two potential reasons for this underestimation are incorrect specification of the multiyear land use change scenario and the inaccurate prescription of seasonal cycles of crops in GCMs.

Received 12 May 2006; accepted 22 November 2006; published 15 May 2007.

Keywords: Australia; land use change; radiative forcing.

http://www.agu.org/pubs/crossref/2007/2006JD007505.shtml

I have previously posted comments about this paper, published in the Journal of Quaternary Science that provides evidence for the generally cooler period known as the Little Ice Age being a global phenomenon rather than being limited to the Northern Hemisphere:

Five centuries of climate change in Australia: the view from underground

Henry N. Pollack 1 *, Shaopeng Huang 1, Jason E. Smerdon 2
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA
2Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA

Published Online: 27 Sep 2006

Keywords
palaeoclimate • borehole temperatures • Australia

Summary and conclusions

We have analysed 57 borehole temperature profiles from across Australia to reconstruct a ground surface temperature history for the past five centuries. The five-hundred-year reconstruction is characterised by a temperature increase of approximately 0.5 K, with most of the warming occurring in the 19th and 20th centuries. The 17th century was the coolest interval of the five-century reconstruction, perhaps representing a muted expression of the Little Ice Age widely observed in the Northern Hemisphere. Because most of the boreholes were logged prior to 1976, the observed subsurface temperatures do not show the strong warming experienced by Australia in the last two decades of the 20th century. Comparison of the geothermal reconstruction to the high-quality Australian annual SAT (Surface Air Temperature) time series in their period of overlap shows excellent agreement. The full geothermal reconstruction also shows excellent agreement with the low-frequency component of dendroclimatic reconstructions from Tasmania and NewZealand. The warming of Australia over the past five centuries has been about two-thirds that experienced by southern Africa, and only about half that experienced by the continents of the Northern Hemisphere in the same time interval.

This paper provides evidence for different regional responses to global climate change and illustrates the fact that the world has warmed since the end of the LIA, with half of the warming occurring in the 20th century.