The CO2 problem in 6 easy steps

We often get requests to provide an easy-to-understand explanation for why increasing CO₂ is a significant problem without relying on climate models and we are generally happy to oblige. The explanation has a number of separate steps which tend to sometimes get confused and so we will try to break it down carefully.

Step 1: There is a natural greenhouse effect.

The fact that there is a natural greenhouse effect (that the atmosphere restricts the passage of long wave (LW) radiation from the Earth’s surface to space) is easily deducible from i) the mean temperature of the surface (around 15ºC) and ii) knowing that the planet is roughly in radiative equilibrium. This means that there is an upward surface flux of LW around [tex]\sigma T^4[/tex] (~390 W/m²), while the outward flux at the top of the atmosphere (TOA) is roughly equivalent to the net solar radiation coming in (1-a)S/4 (~240 W/m²). Thus there is a large amount of LW absorbed by the atmosphere (around 150 W/m²) – a number that would be zero in the absence of any greenhouse substances.

Step 2: Trace gases contribute to the natural greenhouse effect.

The fact that different absorbers contribute to the net LW absorption is clear from IR spectra taken from space which show characteristic gaps associated with water vapour, CO₂, CH₄, O₃ etc (Harries et al, 2001; HITRAN). The only question is how much energy is blocked by each. This cannot be calculated by hand (the number of absorption lines and the effects of pressure broadening etc. preclude that), but it can be calculated using line-by-line radiative transfer codes. The earliest calculations (reviewed by Ramanathan and Coakley, 1979) give very similar results to more modern calculations (Clough and Iacono, 1995), and demonstrate that removing the effect of CO₂ reduces the net LW absorbed by ~14%, or around 30 W/m₂. For some parts of the spectrum, IR can be either absorbed by CO₂ or by water vapour, and so simply removing the CO₂ gives only a minimum effect. Thus CO₂ on its own would cause an even larger absorption. In either case however, the trace gases are a significant part of what gets absorbed.

Step 3: The trace greenhouse gases have increased markedly due to human emissions

CO₂ is up more than 30%, CH₄ has more than doubled, N₂O is up 15%, tropospheric O₃ has also increased. New compounds such as halocarbons (CFCs, HFCs) did not exist in the pre-industrial atmosphere. All of these increases contribute to an enhanced greenhouse effect.

Step 4: Radiative forcing is a useful diagnostic and can easily be calculated

Lessons from simple toy models and experience with more sophisticated GCMs suggests that any perturbation to the TOA radiation budget from whatever source is a pretty good predictor of eventual surface temperature change. Thus if the sun were to become stronger by about 2%, the TOA radiation balance would change by 0.02*1366*0.7/4 = 4.8 W/m² (taking albedo and geometry into account) and this would be the radiative forcing (RF). An increase in greenhouse absorbers or a change in the albedo have analogous impacts on the TOA balance. However, calculation of the radiative forcing is again a job for the line-by-line codes that take into account atmospheric profiles of temperature, water vapour and aerosols. The most up-to-date calculations for the trace gases are by Myhre et al (1998) and those are the ones used in IPCC TAR and AR4.

These calculations can be condensed into simplified fits to the data, such as the oft-used formula for CO2: RF = 5.35 ln(CO₂/CO₂_orig) (see Table 6.2 in IPCC TAR for the others). The logarithmic form comes from the fact that some particular lines are already saturated and that the increase in forcing depends on the ‘wings’ (see this post for more details). Forcings for lower concentration gases (such as CFCs) are linear in concentration. The calculations in Myhre et al use representative profiles for different latitudes, but different assumptions about clouds, their properties and the spatial heterogeneity mean that the global mean forcing is uncertain by about 10%. Thus the RF for a doubling of CO₂ is likely 3.7±0.4 W/m2 – the same order of magnitude as an increase of solar forcing by 2%.

There are a couple of small twists on the radiative forcing concept. One is that CO₂ has an important role in the stratospheric radiation balance. The stratosphere reacts very quickly to changes in that balance and that changes the TOA forcing by a small but non-negligible amount. The surface response, which is much slower, therefore reacts more proportionately to the ‘adjusted’ forcing and this is generally what is used in lieu of the instantaneous forcing. The other wrinkle is depending slightly on the spatial distribution of forcing agents, different feedbacks and processes might come into play and thus an equivalent forcing from two different sources might not give the same response. The factor that quantifies this effect is called the ‘efficacy’ of the forcing, which for the most part is reasonably close to one, and so doesn’t change the zeroth-order picture (Hansen et al, 2005). This means that climate forcings can be simply added to approximate the net effect.

The total forcing from the trace greenhouse gases mentioned in Step 3, is currently about 2.5 W/m², and the net forcing (including cooling impacts of aerosols and natural changes) is 1.6±1.0 W/m² since the pre-industrial. Most of the uncertainty is related to aerosol effects. Current growth in forcings is dominated by increasing CO₂, with potentially a small role for decreases in reflective aerosols (sulphates, particularly in the US and EU) and increases in absorbing aerosols (like soot, particularly from India and China and from biomass burning).

Step 5: Climate sensitivity is around 3ºC for a doubling of CO₂

The climate sensitivity classically defined is the response of global mean temperature to a forcing once all the ‘fast feedbacks’ have occurred (atmospheric temperatures, clouds, water vapour, winds, snow, sea ice etc.), but before any of the ’slow’ feedbacks have kicked in (ice sheets, vegetation, carbon cycle etc.). Given that it doesn’t matter much which forcing is changing, sensitivity can be assessed from any particular period in the past where the changes in forcing are known and the corresponding equilibrium temperature change can be estimated. As we have discussed previously, the last glacial period is a good example of a large forcing (~7 W/m² from ice sheets, greenhouse gases, dust and vegetation) giving a large temperature response (~5 ºC) and implying a sensitivity of about 3ºC (with substantial error bars). More formally, you can combine this estimate with others taken from the 20th century, the response to volcanoes, the last millennium, remote sensing etc. to get pretty good constraints on what the number should be. This was done by Annan and Hargreaves (2006), and they come up with, you guessed it, 3ºC.

Converting the estimate for doubled CO₂ to a more useful factor gives ~0.75 ºC/(W/m²).

Step 6: Radiative forcing x climate sensitivity is a significant number

Current forcings (1.6 W/m₂) x 0.75 ºC/(W/m²) imply 1.2 ºC that would occur at equilibrium. Because the oceans take time to warm up, we are not yet there (so far we have experienced 0.7ºC), and so the remaining 0.5 ºC is ‘in the pipeline’. We can estimate this independently using the changes in ocean heat content over the last decade or so (roughly equal to the current radiative imbalance) of ~0.7 W/m², implying that this ‘unrealised’ forcing will lead to another 0.7×0.75 ºC – i.e. 0.5 ºC.

Additional forcings in business-as-usual scenarios range roughly from 3 to 7 W/m² and therefore additional warming (at equilibrium) would be 2 to 5 ºC. That is significant.

Always Bet On Stupid

Always Bet On Stupid

by Tim F.

A week or two back NPR gave some guy about three minutes to complain about how the climate community silenced his breakthrough research on snow patterns in the Sierra Nevada mountains. You see, most warming models predict that snowfall will eventually go up in the Sierra Nevadas. The guy (I forget his name) found that it didn’t. QED, global warming is wrong and he can prove it if only academia’s cruel gatekeepers would let his paper into a major journal. NPR then gave about one minute to a gatekeeper who pointed out that the result has already been published five times.

And so it goes. Frankly, as a practicing scientist I am impressed at how well the climate community at East Anglia looks after angry critics have presumably picked through every email dating back to 1996 and published the most embarrassing selections. Look at it this way. In the course of two graduate degrees and a postdoc I have worked at Universities with reputations ranging from exemplary to very good, yet off the top of my head I can think of a couple of scandals that made the news, others that the University resolved internally and a small number more that did or did not get handled informally. I cannot think of a single department that would smell like roses if someone stole twelve years of private correspondence and released a selection of emails calibrated to make it look bad. Science works fine in aggregate, but this idea that science must have only flawless people doing impeccable work is a strawman set up by the superstitious to discredit empiricism through nutpicking.

As far as I can tell from Kevin Drum’s summary, other than the question of whether researchers deleted some emails that might have fallen under a Freedom of Information request the entire controversy boils down to non-experts misinterpreting ordinary communication in bad faith. That FOIA question, however, is worth talking about. Can you interfere with a Freedom of Information request? No, you can’t. That sounds like misconduct. Fortunately universities have mechanisms to deal with misconduct. Most will mediate a dozen or so exactly like this in a typical year. It seems to me that even if the emails were hacked illegally, East Anglia should still hold the appropriate hearings. If anyone involved did wrong then impose the appropriate sanction (usually ranging from a written reprimand to a limited ban on publication or grant applications). Maybe other scientists think that I’m granting too much to an angry mob. If so, fine. I try pretty hard to keep my personal sympathies separate when it comes to questions of misconduct and punishment.

Separately, Drum links to a complaint about East Anglia’s PR.

I have seldom felt so alone. Confronted with crisis, most of the environmentalists I know have gone into denial. The emails hacked from the Climatic Research Unit (CRU) at the University of East Anglia, they say, are a storm in a tea cup, no big deal, exaggerated out of all recognition. It is true that climate change deniers have made wild claims which the material can’t possibly support (the end of global warming, the death of climate science). But it is also true that the emails are very damaging.

....The crisis has been exacerbated by the university’s handling of it, which has been a total trainwreck: a textbook example of how not to respond….When the emails hit the news on Friday morning, the university appeared completely unprepared. There was no statement, no position, no one to interview. Reporters kept being fobbed off while CRU’s opponents landed blow upon blow on it. When a journalist I know finally managed to track down Phil Jones, he snapped “no comment” and put down the phone. This response is generally taken by the media to mean “guilty as charged”.

....The handling of this crisis suggests that nothing has been learnt by climate scientists in this country from 20 years of assaults on their discipline. They appear to have no idea what they’re up against or how to confront it. Their opponents might be scumbags, but their media strategy is exemplary.

The complaint here is both fair and unfair. One the one hand one can hardly deny that East Anglia shot itself in the groin when the story bubbled for so long without their input. But really, what did you expect would happen? We pay scientists to do science. Especially given the effort that it takes to talk intelligently about climate science*, we don’t pay them very much. I have worked on grants from NOAA, the agency that also funds climate research. The idea of our lab or our department retaining a worthwhile PR firm would certainly amuse the staff who scrambled every year to find money for cookies and coffee at our weekly seminars. The money for scientists to do anything that isn’t science just isn’t there. If you want professional PR to defend science then you have to fund it with something other than the grants that fund the science itself. Forcing researchers with a day job to act as the front line against Exxon’s army of professional denial firms, in the media, is ridiculous and sad. It’s like asking Sidney Crosby to defend Pittsburgh by way of competitive corndog eating.

Especially early in this story’s life cycle, when you could hardly expect an average reporter to make much sense of the science, a sheaf of personality stories (e.g.) complained about the defensive attitude among climate researchers. Again, you have to wonder what people expect. Taken collectively the “science” of warming denial has exactly as much credibility as the anti-evolution brigades. Their ideas amount to a series of turds thrown indiscriminately at the wall (solar forcing, natural cycles, the world is really cooling et cetera ad nauseum) in the hope that something might stick. The same people come back over and over with a new argument every year, as if the argument they made last year (which also proved beyond a shadow of a doubt that carbon-forced climate warming is a hoax) was just a practice round. It should not stretch the imagination to see how a professional scientist could get jaded after decades of attack by angry hysterics who, almost to a man, lack the training to understand what they are talking about (note: meteorologist means “weatherman”).

Congrats to King Pyrrhus

What really confuses me is why the denial crowd is still so angry about this. They already got what they need. The East Antarctic Ice Sheet started to melt this year, and that was the stable half of Antarctica. That arctic ice that deniers like our own BOB have crowed about turned out to be a thin, temporary layer that hid a dramatic loss of once-permanent arctic sea ice. Outside of a very few exceptions (some very cold regions, where warming will not make much difference, have seen increased snowfall), glaciers are shrinking everywhere on Earth.

Let’s say that everyone agreed with the IPCC conclusions tomorrow. Even better, let’s say that everyone agreed with the bulk of climate scientists who think that the IPCC has been far too conservative (actual warming consistently breaks IPCC hundred-year forecasts in five or ten). What do we do? The climate has a decade of intertia built into it. Current models that describe what would happen if we cut our emissions back to the stone age are still scary as hell.

Climate deniers never had to hold out forever. They just needed confusion to last long enough that cutting carbon to keep the climate stable no longer made any sense. It worked! Keeping the public confused for a couple more years won’t do much more at this point. So why the grumpy act? Typical rightwingers, I guess, angry when they’re losing and twice as angry when they win.

(*) Not kidding about this. A set of courses that roughly introduced climate science, required for my Master’s in Oceanography, nearly wiped me out. That semester I learned exactly how many hours of sleep one needs on a continual basis to stay functionally alert (four).

Climate Change: The Role of Flawed Science

Eelmine nädal postitas RealClimate.org neile mõni aeg tagasi saadetud prof. Peter Laut kirja, milles ta avaldab imestust ja pahameelt, et ikka ja jälle tõuseb esile "päike" kui kliimasoojenemise süüdlane. Tema olla korduvalt selle teooria ilma vastuväideteta põhja lasknud kuid sellegipoolest on jälle jälle kuulda päikeseordu sõnuvõttu. Mis toimub teil seal kliimateaduses, küsib ta murelikult.

Kirja tasub lugeda kuna on sisult teadusfilosoofiline.


We received a letter with the title ‘Climate Change: The Role of Flawed Science‘ which may be of interest to the wider readership. The author, Peter Laut, is Professor (emeritus) of physics at The Technical University of Denmark and former scientific advisor on climate change for The Danish Energy Agency. He has long been a critic of the hypothesis that solar activity dominates the global warming trend, and has been involved in a series of heated public debates in Denmark. Even though most of his arguments concern scientific issues, such as data handling, and arithmetic errors, he also has much to say about the way that the debate about climate change has been conducted. It’s worth noting that he sent us this letter before the “CRU email” controversy broke out, so his criticism of the IPCC for being too even handed, is ironic and timely.

Solar activity & climate: is the sun causing global warming?

The skeptic argument...

Over the past few hundred years, there has been a steady increase in the numbers of sunspots, just at the time when the Earth has been getting warmer. The data suggests changing solar activity is influencing in some way the global climate causing the world to get warmer (BBC).

What the science says...

Solar activity has shown little to no long term trend since the 1950's. Consequently, any correlation between sun and climate ended in the 1970's when the modern global warming trend began.

As supplier of almost all the energy in Earth's climate, the sun certainly has a strong influence on climate change. Consequently there have been many studies examining the link between solar variations and global temperatures.

The correlation between solar activity and temperature

The most commonly cited study by skeptics is a study by scientists from Finland and Germany that finds the sun has been more active in the last 60 years than anytime in the past 1150 years (Usoskin 2005). They also found temperatures closely correlate to solar activity.

However, a crucial finding of the study was the correlation between solar activity and temperature ended around 1975. At that point, temperatures rose while solar activity stayed level. This led them to conclude "during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source."

In other words, the study most quoted by skeptics actually concluded the sun can't be causing global warming. Ironically, the evidence that establishes the sun's close correlation with the Earth's temperature in the past also establishes it's blamelessness for global warming today.

Other studies on solar influence on climate

This conclusion is confirmed by many studies quantifying the amount of solar influence in recent global warming:

• Erlykin 2009: "We deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to solar activity is 14% of the observed global warming"
• Benestad 2009: "Our analysis shows that the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980."
• Lockwood 2008: "It is shown that the contribution of solar variability to the temperature trend since 1987 is small and downward; the best estimate is −1.3% and the 2σ confidence level sets the uncertainty range of −0.7 to −1.9%."
• Lockwood 2008: "The conclusions of our previous paper, that solar forcing has declined over the past 20 years while surface air temperatures have continued to rise, are shown to apply for the full range of potential time constants for the climate response to the variations in the solar forcings."
• Ammann 2007: "Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century."
• Lockwood 2007: "The observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanism is invoked and no matter how much the solar variation is amplified."
• Foukal 2006 concludes "The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global warming over the past 30 years."
• Scafetta 2006 says "since 1975 global warming has occurred much faster than could be reasonably expected from the sun alone."
• Usoskin 2005 conclude "during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source."
• Solanki 2004 reconstructs 11,400 years of sunspot numbers using radiocarbon concentrations, finding "solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades".
• Haigh 2003 says "Observational data suggest that the Sun has influenced temperatures on decadal, centennial and millennial time-scales, but radiative forcing considerations and the results of energy-balance models and general circulation models suggest that the warming during the latter part of the 20th century cannot be ascribed entirely to solar effects."
• Stott 2003 increased climate model sensitivity to solar forcing and still found "most warming over the last 50 yr is likely to have been caused by increases in greenhouse gases."
• Solanki 2003 concludes "the Sun has contributed less than 30% of the global warming since 1970".
• Lean 1999 concludes "it is unlikely that Sun–climate relationships can account for much of the warming since 1970".
• Waple 1999 finds "little evidence to suggest that changes in irradiance are having a large impact on the current warming trend."
• Frolich 1998 concludes "solar radiative output trends contributed little of the 0.2°C increase in the global mean surface temperature in the past decade"

Ocean Thermal Inertia

Usoskin 2005 also found that over 1150 years, temperature lagged solar activity by 10 years. Due to ocean thermal inertia, it takes the climate a decade to catch up to long term changes in solar activity. This is exactly what's observed in the 20th century - in the early decades, solar activity rose sharply with temperature lagging a decade behind. When solar activity leveled out in the 40's, so too did global temperatures.

Kas see on õlitööstuste propaganda, et undermine'ida 97% teadlaste AGW konsensust?

Küsimus Cinoomile kui rohkem kursis olevale.

http://epw.senate.gov/public/index.cfm?FuseAction=Minority.Blogs&ContentRecord_id=2158072e-802a-23ad-45f0-274616db87e6

Cinoom vastab:
Selle küsitluse taga on senaator Jim Inhofe, kellest tuleb teha eraldi postitus. Tema ettevõtmised on seda väärt. Tema kohta vaata infot wikist.

James Mountain "Jim" Inhofe (born November 17, 1934) is an American politician from Oklahoma. A member of the Republican Party, he currently serves as the senior Senator from Oklahoma. He is among the most vocal global warming skeptics in Congress.^[1] Inhofe often cites the Bible as the source for his positions on various political issues.^[2]

ja nüüd üks hea demonstratsioon antud küsitlusest:

I have previously debunked the absurd list of Sen. James Inhofe (R-OK) with over 400 names of supposedly “prominent scientists” who supposedly “recently voiced significant objections to major aspects of the so-called consensus’ on man-made global warming.” So had many others (and here and here).

At Grist, climate scientist Andrew Dessler, has continued running “The ‘Inhofe 400′ Skeptic of the Day” repeatedly identifying some skeptics who were completely unqualified and others who are qualified but not actually skeptical. His latest posting is so good, parts deserves repeating here. Meteorologist George Waldenberger is on the list. In response, George sent an email to Inhofe’s staffers that began:

Take me off your list of 400 (Prominent) Scientists that dispute Man-Made Global warming claims. I’ve never made any claims that debunk the “Consensus”.

You quoted a newspaper article that’s main focus was scoring the accuracy of local weathermen. Hardly Scientific … yet I’m guessing some of your other sources pale in comparison in terms of credibility.

You also didn’t ask for my permission to use these statements. That’s not a very respectable way of doing “research”.

Yet, as Dessler notes, “he’s still on the list.” Dessler’s other conclusions:

Second, the more I look through this list, the more it perfectly demonstrates the weakness of the skeptics. The AGU, for example, has 50,000 members, the majority of whom are Ph.D. Earth scientists. Inhofe would have been tickled pink to take any one of them. But he couldn’t. Despite the huge numbers of qualified scientists out there, Inhofe could barely muster a few dozen for his list.

As a result, Inhofe was forced to include on this list people with zero qualifications as well as people who are not actually skeptics. In the end, I estimate that his list is 80-90 percent bogus — which leaves a few dozen credible climate skeptics on the list. Hmm, just what I’ve been saying all along.

Third, several commenters here as well as other websites have taken it upon themselves to look at the qualifications of the authors of the IPCC. Despite their best efforts, none of them has been able to provide names of any authors of the working group 1 report that are similarly unqualified.

It seems that a careful analysis of the situation shows clearly that the scientific consensus is as robust as ever. Keep tryin’, Jim.

My only disagreement with Dessler: I’d end by saying “Stop tryin’, Jim — please!”

Is There Agreement Amongst Climate Scientists on the IPCC AR4 WG1?

Is There Agreement Amongst Climate Scientists on the IPCC AR4 WG1?

Filed under: Climate Science Reporting — Roger Pielke Sr. @ 7:00 am

One of the readers of Climate Science (Fergus Brown), in response to the questions that have been raised by the weblog (and elsewhere)  wanted to poll the climate community to ascertain their views on the IPCC WG1 report.  The article that we completed on this subject, under his leadership, is given in its entirety later in this weblog.  However, a brief history as to why we are publishing as a weblog and not in another venue is discussed below.
After the survey was completed last summer and the article written, it was submitted to the AGU publication EOS as a “Forum piece. The EOS description of a Forum is that it
 ”contains thought-provoking contributions expected to stimulate further discussion, within the newspaper or as part of Eos Online Discussions. Appropriate Forum topics include current or proposed science policy, discussion related to current research in our fields especially scientific controversies, the relationship of our science to society, or practices that affect our fields, science in general, or AGU as an organization. Commentary solely on the science reported in research journals is not appropriate.”
Our article certainly fits this description.  However, after 4 months without a decision, our contribution was summarily rejected by Fred Spilhous without review. He said our article did not fit EOS policy. We disagreed, of course, based on the explicit EOS policy given above, but our follow request for an appeal was ignored.
We then submitted to Nature Precedings where their policy states
“Nature Precedings is a place for researchers to share pre-publication research, unpublished manuscripts, presentations, posters, white papers, technical papers, supplementary findings, and other scientific documents. Submissions are screened by our professional curation team for relevance and quality, but are not subjected to peer review. We welcome high-quality contributions from biology, medicine (except clinical trials), chemistry and the earth sciences.”
Our article was quickly rejected without explanation.
From this experience, it is clear that the AGU EOS and Nature Precedings Editors are using their positions to suppress evidence that there is more diversity of views on climate, and the human role in altering climate, than is represented in the narrowly focused 2007 IPCC report.  
Our article follows below. We invite colleagues who are expert in polling techniques to build on the polling questions that we pose in our contribution, and to provide the community and policymakers with the actual range of perspectives on climate science.
Our paper is
Brown, F., J. Annan, and R.A. Pielke Sr., 2008: Is there agreement amongst climate scientists on the IPCC AR4 WG1?
Fergus W.M. Brown, CPE, UCLAN, Preston, UK
Roger A. Pielke Sr. CIRES, University of Colorado, Boulder, CO
James D. Annan, FRCGC/JAMSTEC, Yokohama, Japan


Et läbu vähem oleks, toon siia vaid nende läbiviidud küsitluse kokkuvõtte:
"In conclusion, there is strong agreement on the important role of  radiative forcing due to human
additions of CO2 on AGW. However, the relative role of this forcing, in comparison to other human
climate forcings, is still an open scientific question. Thus, those who claim that the radiative effect
of human added CO2 is unimportant are not supported in our poll of climate scientists. However, a
significant minority of 15-20% take the view that the IPCC does exaggerate the relative role of this
forcing.

An important inference from these conclusions is that there continues to be an important debate
about the correct attribution of forcings which should be clearly expressed as an area of uncertainty
to policy makers in the relevant scientific summaries, and that there remains a strong case for
continued investment and investigation into this area of climate research. "

IPCC Fourth Assessment Report (AR4)

Climate Change 2007: The Physical Science Basis

Climate Change 2007: Impacts, Adaptation and Vulnerability

Climate Change 2007: Mitigation of Climate Change

ma ei tea kas uuemat tegevuskava on välja töötatud