Frosty attitudes to Global warming

It seems that the issue of global warming is a contentious issue amongst many people. What surprises me the most though is peoples ignorance on our earths history and the more serious- and likely threat- of global cooling which, were it not for our human omissions, would likely be in an accelerated state and pose a far greater threat than the ominous and largely government body endorsed theory of global warming.

In a nutshell I have done my homework and read more than a few internet pages on the topic. I have a moderate to good historical understanding of the earths behaviour over the last several millions of years and am well aware of just how uninhabitable this planet generally is. The thing that I find the most surprising is that most people seem to think this planet is generally serene and pleasant when the truth is quite the opposite, whatever we do or do not do in terms of our C02 omissions this earth will once again, as it has done so many times before, react in a way that is not conducive to human life. Whether we go through another great freeze, a colossal flooding or a heat wave to rival dominoes pizza's warm delivery technology matters little. The point is people ought to take the time to study up on their history, and by history I do not just mean the bits that include our existence. This would be most helpful, so you do not look foolish.

In the meantime, and to clarify, It is important for mankind's evolution and progress that we invest in cleaner and more abundant energy sources, that we do more to protect the fragile lungs of our own kind and all other species on this planet and that we always seek to better our methods and reduce pollution. But make no mistake, this planet is in no danger, it has survived much greater viruses and attacks than the scourge of mankind. It is ourselves we need to worry about and of course in order to prepare for when this earth goes back to her usual behaviour of temper tantrums we need to think ahead and make changes; but I for one will not buy into a theory endorsed primarily only by government funded scientists in much the same way as I would not trust the general body of any institution or group who has such binding ties to governments known for their pathological habit of deception, propaganda and outright fraud. Almost all of the information you will find online in regards to the fear mongering of global warming leads back to the pockets of governments with obvious agendas for pushing such oblique and shaky science. Believe what you will, but just coz the ice caps are melting that does not necessarily mean we are to blame. They have done this before you know and it didn't require our help whatsoever.

Below is an intelligent response from a forum poster whose views and research I share. His comments, worded well and backed up by fact, mirror my own:-

I have read Bill Bryson's book[The book he is refering to is 'A brief history of nearly everything' which is a very good book.], a great book in fact, and I was most interested in the information concerning other carbon dioxide contributors. The biggest being decaying vegetation, and spewing volcanoes. Humans contribute roughly 7 billion tons of CO2 each year, whereas a volcanic venting, even without eruptions can pump out over 200 billion tons each year. The oceans are an incredible absorber, and forests less so. Carbon dioxide is in the air, there is a lot of it. Whether we are getting warmer or not, or if we have tipped the scale somehow with our paltry contributions since the start of the Industrial Revolution (the famous hockey stick chart), is not the real issue. The question we should be asking ourselves is: Can we adapt? The planet itself is far from danger, so any Save the Planet people need to reassess their focus. We are out to save ourselves. I'm all about keeping song birds, grey wolves, and bengal tigers on the map, but lets face the facts: roughly 25 of the billions of species on this planet go extinct everyday. A drop in the bucket. Human intervention, for better or worse, can pump that number up to the hundreds, but it is still nothing. We should wonder why we need these creatures. Ecosystems are based on a balance, and once certain organisms are extracted from the equation, those species sharing that environment can either benefit from, or be doomed by their absence. Hence, a domino effect. Remove wolves, deer and rabbit populations skyrocket; vegetation decreases; other weaker animals are forced out, the ecosystem may fail in a matter of months, years, or decades.
The planet has been blasted by asteroids, endured tsunami after tsunami, earth shattering earthquakes, sun-blotting supervolcanic eruptions, solar flares, ice ages, polar shifts, mass extinctions by super heat, or super cold. All this over the course of 3 to 4 billion years, and we have the gall to say we have a profound effect on what is happening to the planet. Sorry, but only in relation to ourselves. We're insignificant beings, who have only recently, for the past couple hundred years, had any considerable impact. Think about that.

For more indepth analysis and many links to more grounded and sensible research please go here....below I paste a crude copy of the webpage without active links or illustrations:-

"What If All the Ice Melts?" Myths and Realities

by Wm. Robert Johnston
last updated 29 December 2005

"If we keep using cars, the ice caps will melt and we'll all drown!" This is a myth, just as false as fearing the Sun will die as a result of using solar power. However, as often as I hear it--particularly from people who should know better--I thought I would address it here. First, here is a summary of the facts:

Despite what you may have been told, it has NOT been proven that human-caused global warming is occurring, and in fact there is substantial reason to reject such claims.
The best explanation for the evidence is that whatever global warming trend exists is mostly the result of natural influences like variations in the climate system and variations in solar radiation.
The suggestions that human activities will cause significant changes in global temperature and sea level in the next century are flawed predictions which haven't been confirmed by observations.
The solutions to this apparently non-existent problem proposed by environmentalists would not have a significant effect on climate, but they would cause a significant amount of human suffering.
Based on what we know now, in the next 100 years a rise in sea level of 0.1 meters (4 inches) would not be surprising; those predicting changes of 0.5-2 meters (1.5-7 feet) are using flawed models.
If all the icecaps in the world were to melt, sea level would rise about 60-75 meters (200-250 feet). This could not result from modern human activities, and from any realistic cause would take thousands of years to occur.

I have discussed the first four points (which are non-trivial and deserve extended discussion) in Global warming, Some scientific data on global climate change, and "Facts disprove warnings about global warming", and the fifth point in Facts and figures on sea level rise. I will mostly address the last point--not just to dispel the notion that we need worry, but also because it is a valid and interesting thing to be curious about.

I. The world's ice

Currently the Earth has permanent ice in the icecaps of Antarctica and Greenland, plus much smaller permanent glaciers in various mountain regions of the world. This ice is "permanent", however, only over the short timespan of modern human civilization. Additionally there are two large ice sheets floating in seas off Antarctica, plus floating pack ice in the Arctic Ocean and surrounding Antarctica. Geological evidence indicates very clearly that at times in the Earth's past icecaps were much larger in extent--and alternately, at other times icecaps were virtually nonexistent.

Currently there are about 30,000,000 cubic kilometers of ice in the world's icecaps and glaciers. This volume of ice is fairly well measured (within 5-15%) by surveying the top of the icecaps with methods like radar and laser altimetry, locating the bottom of the ice with methods like seismic soundings, and calculating the difference. A breakdown is as follows:

World ice inventory

Location Volume (km3) Fraction of
world ice Change in volume
since 1960 (km3) ** comments
Continental glaciers and ice fields* 87,000 (± 10,000) [1] 0.29 % -4,700 [2,3,4] grounded
Greenland ice cap 2,930,000 (2,620,000 to 3,000,000) [5,6,7,8,9] 9.8 % -2,000 [6,10,11,12,13,14] grounded
Greenland continental glaciers ~50,000 (± 20,000?) [15] 0.17 % -350 [3,4] grounded
Arctic Ocean pack ice 16,000 summer, 24,000 winter [16,17] 0.01 % -3,000 [16,18,29] floating
East Antarctic Ice Sheet 23,000,000 (21,800,000 to 26,040,000) [5,6,8,19] 76.8 % +10,000 [6,20,21] grounded
West Antarctic Ice Sheet 3,000,000 (3,000,000 to 3,260,000) [5,19] 10.0 % -4,500 [21,22,23] grounded
Antarctic Peninsula ice cap 227,000 [5,24] 0.76 % (included with EAIS) grounded
Antarctic continental glaciers ~50,000 (± 20,000?) [15] 0.17 % -700 [3,4] grounded
Ross Ice Shelf 230,000 [24] 0.77 % -2,000 [26,27] floating
Ronne-Filcher ice shelves 344,000 [25] 1.17 % -2,000 [26,27] mostly floating
South polar pack ice 4,000 summer, 19,000 winter [28] 0.08 % +100 [28] floating

Total world ice ~29,960,000 100 % -9,150
--grounded ice only ~29,340,000 97.9 % -2,250 grounded
--floating ice only ~620,000 2.1 % -6,900 floating

Notes to table: These values are approximate; sources are given, which have in some cases been indirectly used to estimate volumes; errors in interpretation should be assigned to me, not to the original sources.
* Continental glaciers and ice fields--outside Greenland and Antarctica.
** Changes in volume are very uncertain; these values may be taken as illustrative. In most cases these are measurements over a limited time range extrapolated to the total change in volume from 1960 to 2005. Some values are based on models, not directly on measurements.

Grounded ice is ice resting on the ground rather than floating. The melting of floating ice will not change sea level: the mass of this ice is equal to that of the water it displaces (watch the water level in a cup of floating ice cubes as they melt). For comparison, globally ice (both grounded and floating) represents about 2% of the world's water, with about 1,350,000,000 km3 of water in the oceans.

During the last Ice Age the maximum extent of glaciation was around 16,000 B.C. At that time large ice sheets covered all of Canada, much of the American midwest and northeast, all of Scandinavia and some surrounding regions of Eurasia. The total volume of ice then was perhaps 80,000,000 cubic kilometers, or between two and three times as much as today. Correspondingly, world sea level was about 120 meters lower [6,30].

II. Why melting is not a threat

While today's balance between the icecaps and global sea level has been relatively steady since about 1000 B.C., it would be careless to assume that this is the Earth's natural state and that it should always be this way. What could happen to climate naturally in the next few thousand years? If the Earth continued to warm and break from ice age conditions, some of the remaining ice caps could melt. On the other hand, climate might swing back into another ice age. (In fact, some of the environmentalists now worried about global warming were worried about another ice age in the 1960s and 1970s.)

In either case, such a change in climate would take thousands of years to accomplish. Note that it has taken 18,000 years to melt 60% of the ice from the last ice age. The remaining ice is almost entirely at the north and south poles and is isolated from warmer weather. To melt the ice of Greenland and Antarctica would take thousands of years under any realistic change in climate. In the case of the East Antarctic Ice Sheet, which accounts for 80% of the Earth's current ice, Sudgen argues that it existed for 14,000,000 years, through wide ranges in global climate. The IPCC 2001 report states "Thresholds for disintegration of the East Antarctic ice sheet by surface melting involve warmings above 20° C... In that case, the ice sheet would decay over a period of at least 10,000 years." [31] The IPCC is the United Nations' scientific committee on climate change; its members tend to be the minority that predicts global warming and its statements tend to be exaggerated by administrators before release. Given that the IPCC tends to exaggerate the potential for sea level rise, it is clear that no scientists on either side of the scientific debate on global warming fear the melting of the bulk of Antarctica's ice. Consider also this abstract of an article by Jacobs contrasting scientific and popular understanding:

A common public perception is that global warming will accelerate the melting of polar ice sheets, causing sea level to rise. A common scientific position is that the volume of grounded Antarctic ice is slowly growing, and will damp future sea-level rise. At present, studies supporting recent shrinkage or growth depend on limited measurements that are subject to high temporal and regional variability, and it is too early to say how the Antarctic ice sheet will behave in a warmer world. [32]

This statement alludes to the significant point that the Antarctic ice cap appears to currently be growing rather than shrinking. In fact, were the climate to warm significantly in the next few centuries (not a certain future, but supposing it happened), current models suggest that Antarctica would gain ice, with increased snowfall more than offsetting increased melting.

How much concern should we have about the 20% of world ice outside the East Antarctic Ice Sheet? Some sources have recently discussed the "possible collapse" of the West Antarctic Ice Sheet (WAIS). It is suggested that this sheet (about 10% of Antarctic ice) could melt in the "near term" (a usefully vague phrase) and raise sea level 5 to 6 meters. Current understanding is that the WAIS has been melting for the last 10,000 years, and that its current behavior is a function of past, not current climate. [23] The abstract of an article by Alley and Whillans addresses this:

The portion of the West Antarctic ice sheet that flows into the Ross Sea is thinning in some places and thickening in others. These changes are not caused by any current climatic change, but by the combination of a delayed response to the end of the last global glacial cycle and an internal instability. The near-future impact of the ice sheet on global sea level is largely due to processes internal to the movement of the ice sheet, and not so much to the threat of a possible greenhouse warming. Thus the near-term future of the ice sheet is already determined. However, too little of the ice sheet has been surveyed to predict its overall future behavior. [34]

Similarly, recent stories have periodically appeared concerning the potential receding of the Greenland ice cap. Two points may be made regarding current understanding here. First, there is considerable disagreement as to the current rate of net ice cap loss--or even if there is net loss versus net gain. Second, even with temperature increases far greater than the dubious predictions of the IPCC, models indicate that Greenland's ice cap would take 2,000 to 10,000 years to disappear.

Some discussion of the concerns about near term sea level rise may be found in Facts and figures on sea level rise. The predictions that have been made for ice cap melting in the next century rely mostly on melting of glaciers in mountain regions, not melting of the polar ice caps. Even the pessimistic models cited by the IPCC tend to predict an increase in the volume of the Antarctic ice cap with warmer temperatures due to increased snowfalls. In general temperature changes of a few degrees do not seem to be sufficient to begin to melt the polar ice caps, particularly the Antarctic ice cap.

III. Imagining the world without ice caps

As long as we understand that the polar ice caps are not going to melt in the foreseeable future, we can proceed to imagine what the world would be like if they did melt.

Using the ice volume figures from above it is straightforward to estimate the effect on sea level were all this ice melted. Melting the 29,300,000 km3 of grounded ice would produce 26,100,000 km3 of water. Note that melting of floating ice has no effect on sea level. Also, about 2,100,000 km3 of the grounded ice in Antarctica is below sea level [19] and would be replaced by water. Thus, the net addition to the world's oceans would be about 24,000,000 km3 of water spread over the 361,000,000 km2 area of the world's oceans, giving a depth of 67 meters. The new ocean area would be slightly larger, of course, since some areas now land would be covered with water. The final result would be around 66 meters (current estimates range between 63 and 75 meters).

What would the Earth look like as a result? If sea level were 66 meters higher than today, the result would be as illustrated below (for the map I used below see this page):

Obviously some areas are affected more than others. Some larger areas now underwater are the southeastern United States, part of the Amazon River basin, northern Europe, Bangladesh, parts of Siberia along the Arctic Ocean, and portions of mainland China. A large area in Australia would be below sea level, but it is not joined to the ocean and could remain dry.

Above is a view of the lower 48 states of the United States with a 66-meter-higher sea level. Below are some closeups:

upper left: western Washington state and the Portland, Oregon area;
upper right: Virginia, Maryland, Delaware, and southern New Jersey;
lower left: central California, near San Francisco bay; and
lower right: south Texas, from Corpus Christi to Brownsville.

Both Greenland and Antarctica, free of ice, have areas that would be below sea level. However, with the weight of this ice removed, Greenland and Antarctica would rise higher--this phenomena is called isostatic rebound. This rebound lags behind the removal of the ice (by thousands of years). Eventually, most of Greenland would probably be above sea level. However, significant portions of Antarctica would remain underwater. This is shown below in a view of the southern hemisphere:

Today the Earth has 148 million sq. km of land area, of which 16 million sq. km is covered by glaciers. A sea level rise of 66 meters would flood about 13 million sq. km of land outside Antarctica. Without polar ice, Antarctica and Greenland would be ice free, although about half of Antarctica would be under water. Thus, ice-free land would be 128 million sq. km compared to 132 million sq. km today.

As a result, in terms of total habitable land area, the Earth might have more than today. The coastal areas reclaimed by the sea would be mostly offset by now habitable areas of Greenland and Antarctica. Again, remember that such climate change would take thousands of years. Over such time scales vegetation would be restored to newly ice-free regions even without human activity. Also, vast areas which are now desert and tundra would become more fit for human habitation and agriculture.

The illustrations above do not depict any changes in vegetation. In reality, local climates would be very different in ways that are currently difficult to predict. It might be that the warmer climate would lead to generally greater precipitation (this is suggested by comparison to the last ice age, when cooler temperatures caused expansion of the Sahara). Unfortunately, current models are not reliable enough to give a confident answer.

So why wouldn't people drown? Again, a change in the Earth this dramatic would take thousands of years to effect from any realistic cause. Over generations people would migrate as the coasts changed. Consider that virtually all of the settlements in the United States were established only in last 350 years. Of course, many settlements inhabited for thousands of years would have to be abandoned to the ocean--just as many would have to be abandoned if ice age conditions returned and covered vast areas with ice sheets. But people can comfortably adjust where they live over periods of decades, far shorter than the thousands of years needed for these climate changes to naturally take place. Also, that's if they occur, and we have no evidence to indicate what would happen to climate over the next few thousand years.

IV. A final comment

For those curious as to what the Earth would be like with the ice caps melted, this report has hopefully given an illustration, along with some perspective: this sort of change cannot be affected by modern human activity even given many centuries. It is sad that some youngsters think that burning of hydrocarbons could cause the ice caps to melt and drown cities; it is criminal when teachers don't correct this nonsense. And it should tell you much of environmental groups like the Sierra Club when they use such myths to further an extremist political agenda.

Sources:

[1] Raper, S. C. B., and R. J. Braithwaite, 8 March 2005, "The potential for sea level rise: New estimates from glacier and ice cap area and volume distributions," Geophysical Research Letters, 32:L05502.
[2] National Snow and Ice Data Center, 14 March 2005, "State of the cryosphere: Is the cryosphere sending signals about climate change?", NSIDC, on line [http://nsidc.org/sotc/glacier_balance.html].
[3] Dyurgerov, M., 2002, "Glacier mass balance and regime: Data of measurements and analysis," Institute of Arctic and Alpine Research, on line [http://instaar.colorado.edu/other/occ_papers.html].
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[5] U.S. Geological Survey, 31 Jan. 2000, "Sea level and climate," USGS, on line [http://pubs.usgs.gov/fs/fs2-00/].
[6] Intergovernmental Panel on Climate Change, 2001, Climate Change 2001: The Scientific Basis, section 11.2, on line [http://www.grida.no/climate/ipcc_tar/wg1/].
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[8] Hulbe, C. L., 11 April 1997, "Recent changes to Antarctic Peninsula ice shelves: What lessons have been learned?", on line [http://naturalscience.com/ns/articles/01-06/ns_clh.html].
[9] Bamber, J. L., R. L. Layberry, S. P. Gogenini, 2001, "A new ice thickness and bedrock dataset for the Greenland ice sheet 1: Measurement, data reduction, and errors," Journal of Geophysical Research, 106(D24):3177-3180 [http://nsidc.com/data/docs/daac/nsidc0092_greenland_ice_thickness.gd.html].
[10] Krabill, W. et al., 21 July 2000, "Greenland Ice Sheet: High-elevation balance and peripheral thinning," Science, 289:428-430.
[11] Johannessen, O. M., K. Khvorostovsky, M. W. Miles, and L. P. Bobylev, 11 Nov. 2005, "Recent ice-sheet growth in the interior of Greenland,", Science, 310:1013-1016.
[12] Box, J. E., and D. H. Bromwich, 26 Aug. 2004, "Greenland ice sheet surface mass balance 1991-2000: Application of Polar MM5 mesoscale model and in situ data," Journal of Geophysical Research, 109:D16105.
[13] Hanna, E., et al., 2005, "Runoff and mass balance of the Greenland ice sheet: 1958-2003," Journal of Geophysical Research, 110:D13108 [http://www.awi-bremerhaven.de/Publications/Han2005a_abstract.html].
[14] Velicogna, I., and J. Wahr, 30 Sept. 2005, "Greenland mass balance from GRACE," Geophysical Research Letters, 32:L18505.
[15] Intergovernmental Panel on Climate Change, 2001, Climate Change 2001: The Scientific Basis, section 11.2, on line [http://www.grida.no/climate/ipcc_tar/wg1/].
[16] Goosse, H., R. Gerdes, F. Kauker, and C. Koberle, 2004, "Influence of the exchanges between the Atlantic and the Arctic on sea ice volume variations during the period 1955-97," Journal of Climate, 17:1294-1305.
[17] Linacre, E., and B. Geerts, July 1998, "The Arctic: the ocean, sea ice, icebergs, and climate," Univ. of Wyoming Dept. of Atmospheric Science, on line [http://www-das.uwyo.edu/~geerts/cwx/notes/chap17/arctic.html].
[18] Lindsay, R. W., and J. Zhang, 2005, "The thinning of Arctic sea ice, 1988-2003: Have we passed a tipping point?", Journal of Climate, forthcoming [http://www.uwnews.org/relatedcontent/2005/September/rc_parentID12459_thisID12461.pdf].
[19] Lythe, M. B., D. G. Vaughan, and the BEDMAP Consortium, 10 June 2001, "BEDMAP: A new ice thickness and subglacial topographic model of Antarctica," Journal of Geophysical Research, 106:B6:11335-11351.
[20] Davis, C. H., Yonghong Li, J. R. McConnell, M. M. Frey, and E. Hanna, 24 June 2005, "Snowfall-driven growth in East Antarctic Ice Sheet mitigates recent sea-level rise," Science, 308:1898-1901.
[21] Cazenave, A., and R. S. Nerem, 2004, "Present-day sea level change: Observations and causes," Reviews of Geophysics, 42:RG3001.
[22] Thomas, R., et al., 8 Oct. 2004, "Accelerated sea-level rise from West Antarctica," Science, 306:255-258.
[23] Stone, J. O., et al., 3 Jan. 2003, "Holocene deglaciation of Marie Byrd Land, West Antarctica, Science, 299:99-102.
[24] Drewry, D. J., 1983, Antarctica: Glaciological and Geophysical Folio, Scott Polar Research Institute, Univ. of Cambridge.
[25] Sandhager, H., D. G. Vaughan, and A. Lambrecht, 2004, "Meteoric, marine and total ice thickness maps of Filchner-Ronne-Schelfeis, Antarctica," FRISP Report no. 15 on line [http://rai.ucsd.edu/~helen/Annals_2001/PDF/34A125_Padman_etal_2002_2col.pdf].
[26] British Antarctic Survey, 9 May 2000, "The loss of ice shelves from the Antarctic Peninsula," British Antarctic Survey, on line [http://www.antarctica.ac.uk/Key_Topics/IceSheet_SeaLevel/ice_shelf_loss.html].
[27] British Antarctic Survey, May 2005, "Antarctic Factsheet Geographical Statistics," British Antarctic Survey, on line [http://www.antarctica.ac.uk/Resources/schoolzone/resources/Factsheets/factsheet_geostats_screen.pdf].
[28] Geerts, B., June 1998, "Antarctic sea ice: seasonal and long-term changes," Univ. of Wyoming Dept. of Atmospheric Science, on line [http://www-das.uwyo.edu/~geerts/cwx/notes/chap11/sea_ice.html].
[29] Rothrock, D. A., and J. Zhang, 4 Jan. 2005, "Arctic Ocean sea ice volume: What explains its recent depletion?," Journal of Geophysical Research, 110:C01002.
[30] Bassett, S. E., G. A. Milne, J. X. Mitrovica, and P. U. Clark, 5 Aug. 2005, "Ice sheet and solid earth influences on far-field sea-level histories," Science, 309:925-928.
[31] Intergovernmental Panel on Climate Change, 2001, Climate Change 2001: The Scientific Basis, section 11.5.4.3, on line [http://www.grida.no/climate/ipcc_tar/wg1/].
[32] Jacobs, S. S., 5 Nov. 1992, "Is the Antarctic ice sheet growing?", Nature, 360:29-32.
[33] Sugden, D. E., 1996, "The East Antarctic Ice Sheet: unstable ice or unstable ideas?", Transactions of the Institute of British Geographers, 21:443-454.
[34] Alley, R. B., and I. M. Whillans, 15 Nov. 1991, "Changes in the West Antarctic Ice Sheet", Science, 254:959-962.

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Comments

[Keenan]

Published on Sunday, April 16, 2006 by the San Francisco Chronicle

Scientists Say They're Being Gagged By Bush

White House monitors their media contacts
by Juliet Eilperin

WASHINGTON -- Scientists doing climate research for the federal government say the Bush administration has made it hard for them to speak forthrightly to the public about global warming. The result, the researchers say, is a danger that Americans are not getting the full story on how the climate is changing.

Employees and contractors working for the National Oceanic and Atmospheric Administration, along with a U.S. Geological Survey scientist working at an NOAA lab, said in interviews that over the past year administration officials have chastised them for speaking on policy questions; removed references to global warming from their reports, news releases and conference Web sites; investigated news leaks; and sometimes urged them to stop speaking to the media altogether. Their accounts indicate that the ideological battle over climate-change research, which first came to light at NASA, is being fought in other federal science agencies as well.

These scientists -- working nationwide in research centers in such places as Princeton, N.J., and Boulder, Colo. -- say they are required to clear all media requests with administration officials, something they did not have to do until the summer of 2004. Before then, climate researchers -- unlike staff members in the Justice or State departments, which have long-standing policies restricting access to reporters -- were relatively free to discuss their findings without strict agency oversight.

"There has been a change in how we're expected to interact with the press," said Pieter Tans, who measures greenhouse gases linked to global warming and has worked at NOAA's Earth System Research Laboratory in Boulder for two decades. He said that although he often "ignores the rules" the administration has instituted, when it comes to his colleagues, "some people feel intimidated -- I see that."

Christopher Milly, a hydrologist at the U.S. Geological Survey, said he had problems twice while drafting news releases on scientific papers describing how climate change would affect the nation's water supply.

Once in 2002, Milly said, Interior officials declined to issue a news release on grounds that it would cause "great problems with the department." In November 2005, they agreed to issue a release on a different climate-related paper, Milly said, but "purged key words from the releases, including 'global warming,' 'warming climate' and 'climate change.' ''

Administration officials said they are following long-standing policies that were not enforced in the past. Kent Laborde, a NOAA public affairs officer who flew to Boulder last month to monitor an interview Tans did with a film crew from the BBC, said he was helping facilitate meetings between scientists and journalists.

"We've always had the policy, it just hasn't been enforced," Laborde said. "It's important that the leadership knows something is coming out in the media, because it has a huge impact. The leadership needs to know the tenor or the tone of what we expect to be printed or broadcast."

Several times, however, agency officials have tried to alter what these scientists tell the media. When Tans was helping to organize the Seventh International Carbon Dioxide Conference near Boulder last fall, his lab director told him participants could not use the term "climate change" in conference paper's titles and abstracts. Tans and others disregarded that advice.

None of the scientists said political appointees had influenced their research on climate change or disciplined them for questioning the administration. Several researchers have received bigger budgets in recent years because President Bush has focused on studying global warming rather than curbing greenhouse gases. NOAA's budget for climate research and services is now $250 million, up from $241 million in 2004.

The assertion that climate scientists are being censored first surfaced in January when James Hansen, who directs NASA's Goddard Institute for Space Studies, told the New York Times and the Washington Post that the administration sought to muzzle him after he gave a lecture in December calling for cuts in emissions of carbon dioxide and other greenhouse gases. (NASA Administrator Michael Griffin issued new rules recently that make clear that its scientists are free to talk to members of the media about their scientific findings, including personal interpretations.)

Two weeks later, Hansen suggested to an audience at the New School University in New York that his counterparts at NOAA were experiencing even more severe censorship. "It seems more like Nazi Germany or the Soviet Union than the United States," he told the crowd.

NOAA Administrator Conrad Lautenbacher responded by sending an agency-wide e-mail that said he is "a strong believer in open, peer-reviewed science as well as the right and duty of scientists to seek the truth and to provide the best scientific advice possible."

"I encourage our scientists to speak freely and openly," he added. "We ask only that you specify when you are communicating personal views and when you are characterizing your work as part of your specific contribution to NOAA's mission."

NOAA scientists, however, cite repeated instances in which the administration played down the threat of climate change in their documents and news releases. Although Bush and his top advisers have said that Earth is warming and human activity has contributed to this, they have questioned some predictions and caution that mandatory limits on carbon dioxide could damage the nation's economy.

In 2002, NOAA agreed to draft a report with Australian researchers aimed at helping reef managers deal with widespread coral bleaching that stems from higher sea temperatures. A March 2004 draft report had several references to global warming, including "Mass bleaching ... affects reefs at regional to global scales, and has incontrovertibly linked to increases in sea temperature associated with global change."

A later version, dated July 2005, drops those references and several others mentioning climate change.

NOAA has yet to release the coral bleaching report. James Mahoney, assistant secretary of commerce for oceans and atmosphere, said he decided in late 2004 to delay the report because "its scientific basis was so inadequate." Now that it is revised, he said, he is waiting for the Australian Great Barrier Reef Marine Park Authority to approve it. "I just did not think it was ready for prime time," Mahoney said. "It was not just about climate change -- there were a lot of things."

On other occasions, Mahoney and other NOAA officials have told researchers not to give their opinions on policy matters. Konrad Steffen directs the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder, a joint NOAA-university institute with a $40 million annual budget. Steffen studies the Greenland ice sheet, and when his work was cited last spring in a major international report on climate change in the Arctic, he and another NOAA lab director from Alaska received a call from Mahoney in which he told them not to give reporters their opinions on global warming.

Steffen said that he told him that although Mahoney has considerable leverage as "the person in command for all research money in NOAA ... I was not backing down."

Mahoney said he had "no recollection" of the conversation, which took place in a conference call. "It's virtually inconceivable that I would have called him about this," Mahoney said, though he added: "For those who are government employees, our position is they should not typically render a policy view."

The need for clearance from Washington, several NOAA scientists said, amounts to a "pocket veto" allowing administration officials to block interviews by not giving permission in time for journalists' deadlines.

Ronald Stouffer, a climate research scientist at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, estimated his media requests have dropped in half because it took so long to get clearance to talk from NOAA headquarters. Thomas Delworth, one of Stouffer's colleagues, said the policy means Americans have only "a partial sense" of what government scientists have learned about climate change.

"American taxpayers are paying the bill, and they have a right to know what we're doing," he said.

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