Why are climatologists confident humans are causing global warming?

[gaiasdaughter]

Thank you, Sinimod, for keeping us up to date . . . you and Tony! There is such a wealth of infomation to be found on this site, continously updated. Thanks for all your hard work

[sinimod]

Originally Posted by gaiasdaughter

Thank you, Sinimod, for keeping us up to date . . . you and Tony! There is such a wealth of infomation to be found on this site, continously updated. Thanks for all your hard work

gaiasdaughter, you are most welcome. I, and I know Tony, feel a sense of duty to pass on what we learn about climate change and what is happening to our planet. I know all of us long time manpollo members share a sense of urgency that we want to pass along to new members and visitors to our site; and that the risk to humanity of not acting, that Greg so eloquently explained in his videos and book, is too great.

[sinimod]

Originally Posted by sinimod

In a recent issue of Science (v. 330, October 15, 2010), scientists from the Goddard Institute for Space Studies (GISS) have provided further refinement of the understanding that CO2 is the principal control knob governing the earth’s temperature.

I clicked on the hyperlink above and it didn't work. So here is another attempt to link to the abstract of the article "Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature" by Lacis, Schmidt, Rind, and Ruedy in the journal Science.

[sinimod]

Originally Posted by sinimod

Regarding the GCR theory, the recent Lund et al., 2010 abstract describes the earth's magnetic field intensities during the Laschamp Excursion at less than 10% of normal and persisted for almost 2000 years. This would have been the ideal time for GCR to have noticeably affected the climate. However, in the assessment by Dr. Richard Alley of Penn State University, GCR are merely fine tuning on the climate control knob as heard in his lecture at the American Geophysical Union in San Francisco in 2009. There is really no evidence that there was any global temperature decrease resulting from arguably the largest effect on the magnetic field since the Brunhes-Matuyama magnetic reversal which occurred ~780 ka. To me, this, along with the Calovic et al. article pretty much kills the already seriously crippled GCR theory as a viable theory to account for the global warming.

So, if you remove the solar forcing and GCR theories as possible causes for global warming, where do you run to now?

Ari Jokimäki posted a summary of an article by Erlykin et al., 2011 on the lack of cosmic ray contribution to climate change on his excellent website AGW Observer: Cosmic ray contribution to global warming negligible

There has been claims that cosmic rays could have contributed significantly to global warming. According to a new study that is not the case. Instead, during the last 50 years, cosmic rays seemed to have caused warming of about 0.002°C – a negligible amount compared to observed warming.

Forbush decreases (few percent decrease in cosmic ray flux that lasts few days) have been claimed to cause cloud cover changes. However, the observed correlations between cloud cover changes and cosmic ray flux during a few Forbush decreases could have been coincidental. Additionally, delay between the changes in cosmic ray flux and in cloud cover seems to have been too long for a physical cause. Some of the strongest Forbush decreases have also been associated with strong changes in solar activity, which also places more clouds over the cosmic ray hypothesis.

Nevertheless there are some evidence relating to Forbush decreases that suggests some kind of effect in cloud cover. The strongest effect seems to lie in the stratosphere, but there is also some evidence for an effect in troposphere. It is unclear if these effects are due to cosmic rays or solar activity.

For cosmic ray flux ground level enhancements there also is some evidence of cloud effects. The strongest effect seems to occur in the poles which might suggest genuine cosmic ray involvement. Erlykin et al. estimate a global effect of about 1 % to cloud cover during ground level enhancements.

In a recent analysis it was found out that in mid-latitudes rapid changes in cloud cover are associated with changes in cosmic ray flux and in surface temperature. Strong reaction here only occurs during the rapid cloud cover changes which are rare events, so the total effect of cosmic rays still seems to be small. Here too it is unclear if the observed effects are due to cosmic rays or simultaneous changes in solar activity.

In the case of these rapid changes, the rate of change in clouds and in cosmic rays have been different which speaks against the cosmic ray origin. On the other hand, linking these cloud changes to solar activity is also problematic, because most of the UV radiation stops in the stratosphere and therefore would not be able to cause changes to most of the cloud cover. It is possible that the explanation for cloud changes is found in surface temperature changes caused by solar activity changes.

The correlation of cosmic rays with low cloud cover is the correlation that has been claimed to cause the global warming. However, the spatial distribution of the correlation does not fit to the expectations from cosmic ray origin. Correlation is strong in mid-latitudes, but weak in the poles and in the equator. Mid-latitude correlation is about 8 times higher than the correlation in equator and in poles. This distribution of correlation results a possible effect to global cloud cover which is smaller than 1%.

According to Erlykin et al. the cosmic ray flux has decreased about 0.6% in last 50 years. Assuming 1% effect of the cosmic rays to cloud cover, this would cause a change of 0.002°C in global surface temperature. This is negligible compared to the observed global warming in last 50 years. In conclusion, while cosmic rays do seem to have some minor effects to different things in the atmosphere, they do not seem to have anything to do with global warming.

There are now a plethora of nails in the coffin of the cosmic ray theory as a cause for global warming. The Erlykin et al., 2011 article provides yet another making this coffin securely closed and buried.

[776281]

http://www.jpl.nasa.gov/news/news.cf...s.xml&rst=2934
NASA Study Goes to Earth's Core for Climate Insights
March 09, 2011

The latest evidence of the dominant role humans play in changing Earth's climate comes not from observations of Earth's ocean, atmosphere or land surface, but from deep within its molten core.

Scientists have long known that the length of an Earth day - the time it takes for Earth to make one full rotation - fluctuates around a 24-hour average. Over the course of a year, the length of a day varies by about 1 millisecond, getting longer in the winter and shorter in the summer. These seasonal changes in Earth's length of day are driven by exchanges of energy between the solid Earth and fluid motions of Earth's atmosphere (blowing winds and changes in atmospheric pressure) and its ocean. Scientists can measure these small changes in Earth's rotation using astronomical observations and very precise geodetic techniques.

But the length of an Earth day also fluctuates over much longer timescales, such as interannual (two to 10 years), decadal (approximately 10 years), or those lasting multiple decades or even longer. A dominant longer timescale mode that ranges from 65 to 80 years was observed to change the length of day by approximately 4 milliseconds at the beginning of the 20th century

Still other studies have observed a link between the long-duration variations in Earth's length of day and fluctuations of up to 0.2 degrees Celsius (0.4 degree Fahrenheit) in Earth's long-term global average surface air temperature.

"Our research demonstrates that, for the past 160 years, decadal and longer-period changes in atmospheric temperature correspond to changes in Earth's length of day if we remove the very significant effect of atmospheric warming attributed to the buildup of greenhouse gases due to mankind's enterprise," said Dickey. "Our study implies that human influences on climate during the past 80 years mask the natural balance that exists among Earth's rotation, the core angular momentum and the temperature at Earth's surface."

http://journals.ametsoc.org/doi/abs/...urnalCode=clim
Air Temperature and Anthropogenic Forcing: Insights from the Solid Earth

Jean O. Dickey and Steven L. Marcus

Earth’s rotation rate [i.e., length of day (LOD)], the angular momentum of the core (CAM), and surface air temperature (SAT) all have decadal variability. Previous investigators have found that the LOD fluctuations are largely attributed to core–mantle interactions and that the SAT is strongly anticorrelated with the decadal LOD. It is shown here that 1) the correlation among these three quantities exists until 1930, at which time anthropogenic forcing becomes highly significant; 2) correcting for anthropogenic effects, the correlation is present for the full span with a broadband variability centered at 78 yr; and 3) this result underscores the reality of anthropogenic temperature change, its size, and its temporal growth. The cause of this common variability needs to be further investigated and studied. Since temperature cannot affect the CAM or LOD to a sufficient extent, the results favor either a direct effect of Earth’s core-generated magnetic field (e.g., through the modulation of charged-particle fluxes, which may impact cloud formation) or a more indirect effect of some other core process on the climate—or yet another process that affects both. In all three cases, their signals would be much smaller than the anthropogenic greenhouse gas effect on Earth’s radiation budget during the coming century.

http://moregrumbinescience.blogspot....at-is-day.html
Adds a little more discussion on a what is a day. (More Grumbine Science where I found links to the above articles)

[wibble]

Originally Posted by sinimod

I clicked on the hyperlink above and it didn't work. So here is another attempt to link to the abstract of the article "Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature" by Lacis, Schmidt, Rind, and Ruedy in the journal Science.

Thanks for that link, Sinimod.

I don't see the point in paying to get the full article (I'm pretty confident that the detail would go way over my head).

The abstract is:

Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.

Would it be stupid to ask the question "how might one describe the credibility of this statement alone?"

The page is from sciencemag.com (I'm not familiar with that journal, myself). Is that well respected? There's an AAAS logo, and the site links to aaas.org - does that mean that the content is accredited by the American Association for the Advancement of Science?

The page the abstract is on says:

Received for publication 8 April 2010.
Accepted for publication 10 September 2010.

Is 'accepted for publication' the final hurdle (barring retractions?). Does it mean that it's passed peer review?

There are three other articles that cite this one. Is that a good sign? (I think it is, but then no doubt yer av'rage d'nier will start wibbling about 'groupthink').

I don't really want answers, I'm really just exploring my own ignorance (while thinking of the multitudes who have mistaken faith in the credibility of the 'Oregon Petition' without being aware of the true facts).

I found this blog that claims that the article doesn't reveal anything new (though the typos in that blog post suggest to me that it was written in haste - the author seems over-anxious to point out 'we said it first, in our book').

NASA seems to think it's not wrong.

The bottom line is that atmospheric carbon dioxide acts as a thermostat in regulating the temperature of Earth.

My conclusions:

1. Douglas Adams' white mice are playing with my head again.
2. It's 2:30am. Past my bedtime...

[sinimod]

Currently, there appears to be external and internal forcings that cause global cooling. Active forcings that engender cooling are decreased total solar irradiance, reduction in the concentration of stratospheric water vapor, a possible slight weakening of the Atlantic Meridional Overturning Circulation, the transition to the negative phase of the Pacific Decadal Oscillation, and two of the Milankovitch Cycles that are progressing toward cooling phases and eventually the next ice age. Around the year 2000 the rate of warming might have slowed somewhat, but despite these cooling influences, the planet continues to warm. The globe continues on its warming trend But the rate of warming appears to have temporarily slowed



As is well understood, the total solar irradiance of the sun has decreased during the period of satellite measurements (Lockwood and Frolich, 2007), and sunspot activity has declined since the maximum of solar cycle 19 (reference here).

Solomon etal 2009 reported a significant decline in the concentration of stratospheric water vapor since about 2000. They suggest that this reduction has acted to reduce global temperatures below what they would have been had there been no reduction in stratospheric water vapor concentraion.

Keenlyside etal 2008 has suggested that the Atlantic meridional overturning circulation (AMOC), although conceding that it is difficult to assess, has substantially weakened during the last decade. Based on hindcasting, they maintain that there has been and will continue to be a slowing of the meridional overturning circulation in the Atlantic. Keenlyside etal suggested this has caused a reduction in North Atlantic sea surface temperatures (SST) and the AMOC will continue to weaken, reaching a long-term mean within the next decade. The weakening of the AMOC might contribute a reduction in sea surface temperatures in the North Atlantic Ocean and a concomitant cooling of European and North American surface temperature, although as Lozier, 2010 stated “no observational study to date has been able to successfully link sea-surface temperature changes with overturning changes”.

The Pacific Decadal Oscillation (PDO) has transitioned into its negative phase, which appears to favor La Niña formation (reference here), which promote lower global temperatures. Although there is much doubt for this (see 1940s-1970s revisited?), some scientists believe the PDO was a major cause for the early decline and subsequent flatlining of the 1945-1976 period. If that is the case, this time there has been no decline, but possibly a slowdown in the rate of temperature rise.

On top of all that, the two most important Milankovitch cycles affecting glacial cycles are both tending toward cooling and the gradual descent into another glacial period. The shape of the earth’s orbit is becoming more elliptical, and the tilt is decreasing, both processes favoring colder longer winters in the Northern Hemisphere, thus increasing the probability of ice cover surviving during summers at higher northern latitudes. These orbital processes will continue their cooling influence for literally tens of thousands of years. However, the effects of increased CO2 in the atmosphere could alter climate for over a thousand years, offsetting the cooling influence of the shape of the earth’s orbit around the sun and the tilt of earth’s rotation relative to the plane of the sun’s radiation.

Given all of these processes, the average global temperature should be in significant decline. Yet temperatures continue to rise, although slower than predicted for the last decade. This gives strong testament to the climate forcing power of humanity as the anthropogenically induced increase in atmospheric CO2 and other greenhouse gases, agricultural operations, and changes in land cover have overcome all of the forces currently aligned to cool the planet; and possibly provides testament as to the weak effects of some processes (ie. PDO, solar). As some of these cooling processes change or fade in influence, the rate of temperature increase could skyrocket. Perhaps there is still time to change the way we interact with the planet before the worst effects become inevitable?

[sinimod]

Another cause of cooling not mentioned above is the dramatically increased emissions of sulfur from the growth of Asian industry.

Asia pollution blamed for halt in warming: study

(Reuters) - Smoke belching from Asia's rapidly growing economies is largely responsible for a halt in global warming in the decade after 1998 because of sulfur's cooling effect, even though greenhouse gas emissions soared, a U.S. study said on Monday.

The paper raised the prospect of more rapid, pent-up climate change when emerging economies eventually crack down on pollution.

World temperatures did not rise from 1998 to 2008, while manmade emissions of carbon dioxide from burning fossil fuel grew by nearly a third, various data show.

The researchers from Boston and Harvard Universities and Finland's University of Turku said pollution, and specifically sulfur emissions, from coal-fueled growth in Asia was responsible for the cooling effect.

I think it is unfortunate that they picked 1998 as a year to base their trend on as that year is anomalous and no statistician would ever use such an anomaly in such a way. Nevertheless, the rate of warming has slowed, and in addition to the possible causes listed in the preceding post, this is an additional possible cause for the slow down.

From Yale e360digest:

While carbon dioxide emissions increased by nearly a third from 1998 to 2008, global surface temperatures did not rise sharply during that period. A key reason, researchers said, is that increased sulfur emissions — particularly from coal combustion in Asia, which grew by more than 100 percent during the decade — allowed the formation of aerosols that reflect the sun’s heat back into space, cooling the surface of the Earth. Such effects have long been recognized by scientists studying volcanic eruptions, which in the past have caused cooling and significant crop failures. “Anthropogenic activities that warm and cool the planet largely cancel after 1998, which allows natural variables to play a more significant role,” according to the paper, published in the journal Proceedings of the National Academy of Sciences. That natural cooling effect may abate, however, when nations impose stricter emissions standards, possibly releasing a rapid, pent-up climate change, according to the researchers.

It seems more and more clear that we are living on borrowed time.