Evidence supporting AGW

[Crick]

Detection vs Attribution

Detection and attribution of climate signals, as well as its common-sense meaning, has a more precise definition within the climate change literature, as expressed by the IPCC.[17]

Detection of a signal requires demonstrating that an observed change is statistically significantly different from that which can be explained by natural internal variability.

Attribution requires demonstrating that a signal is:

unlikely to be due entirely to internal variability;
consistent with the estimated responses to the given combination of anthropogenic and natural forcing
not consistent with alternative, physically plausible explanations of recent climate change that exclude important elements of the given combination of forcings.

Detection does not imply attribution, and is easier to show than attribution. Unequivocal attribution would require controlled experiments with multiple copies of the climate system, which is not possible. Therefore, attribution, as described above, can only be done within some margin of error. For example, the IPCC's Fourth Assessment Report says "it is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750," where "extremely likely" indicates a probability greater than 95%.[1]

 

[Crick]

"Fingerprint" Studies

Finally, there is extensive statistical evidence from so-called "fingerprint" studies. Each factor that affects climate produces a unique pattern of climate response, much as each person has a unique fingerprint. Fingerprint studies exploit these unique signatures, and allow detailed comparisons of modelled and observed climate change patterns. Scientists rely on such studies to attribute observed changes in climate to a particular cause or set of causes. In the real world, the climate changes that have occurred since the start of the Industrial Revolution are due to a complex mixture of human and natural causes. The importance of each individual influence in this mixture changes over time. Of course, there are not multiple Earths, which would allow an experimenter to change one factor at a time on each Earth, thus helping to isolate different fingerprints. Therefore, climate models are used to study how individual factors affect climate. For example, a single factor (like greenhouse gases) or a set of factors can be varied, and the response of the modelled climate system to these individual or combined changes can thus be studied.[9]

For example, when climate model simulations of the last century include all of the major influences on climate, both human-induced and natural, they can reproduce many important features of observed climate change patterns. When human influences are removed from the model experiments, results suggest that the surface of the Earth would actually have cooled slightly over the last 50 years (see graph, opposite). The clear message from fingerprint studies is that the observed warming over the last half-century cannot be explained by natural factors, and is instead caused primarily by human factors.[9]

Another fingerprint of human effects on climate has been identified by looking at a slice through the layers of the atmosphere, and studying the pattern of temperature changes from the surface up through the stratosphere (see the section on solar activity). The earliest fingerprint work focused on changes in surface and atmospheric temperature. Scientists then applied fingerprint methods to a whole range of climate variables, identifying human-caused climate signals in the heat content of the oceans, the height of the tropopause (the boundary between the troposphere and stratosphere, which has shifted upward by hundreds of feet in recent decades), the geographical patterns of precipitation, drought, surface pressure, and the runoff from major river basins.[9]

Studies published after the appearance of the IPCC Fourth Assessment Report in 2007 have also found human fingerprints in the increased levels of atmospheric moisture (both close to the surface and over the full extent of the atmosphere), in the decline of Arctic sea ice extent, and in the patterns of changes in Arctic and Antarctic surface temperatures.[9]

The message from this entire body of work is that the climate system is telling a consistent story of increasingly dominant human influence - the changes in temperature, ice extent, moisture, and circulation patterns fit together in a physically consistent way, like pieces in a complex puzzle.[9]

Increasingly, this type of fingerprint work is shifting its emphasis. As noted, clear and compelling scientific evidence supports the case for a pronounced human influence on global climate. Much of the recent attention is now on climate changes at continental and regional scales, and on variables that can have large impacts on societies. For example, scientists have established causal links between human activities and the changes in snowpack, maximum and minimum (diurnal) temperature, and the seasonal timing of runoff over mountainous regions of the western United States. Human activity is likely to have made a substantial contribution to ocean surface temperature changes in hurricane formation regions. Researchers are also looking beyond the physical climate system, and are beginning to tie changes in the distribution and seasonal behaviour of plant and animal species to human-caused changes in temperature and precipitation.[9]

For over a decade, one aspect of the climate change story seemed to show a significant difference between models and observations. In the tropics, all models predicted that with a rise in greenhouse gases, the troposphere would be expected to warm more rapidly than the surface. Observations from weather balloons, satellites, and surface thermometers seemed to show the opposite behaviour (more rapid warming of the surface than the troposphere). This issue was a stumbling block in understanding the causes of climate change. It is now largely resolved. Research showed that there were large uncertainties in the satellite and weather balloon data. When uncertainties in models and observations are properly accounted for, newer observational data sets (with better treatment of known problems) are in agreement with climate model results.[9]

This does not mean, however, that all remaining differences between models and observations have been resolved. The observed changes in some climate variables, such as Arctic sea ice, some aspects of precipitation, and patterns of surface pressure, appear to be proceeding much more rapidly than models have projected. The reasons for these differences are not well understood. Nevertheless, the bottom-line conclusion from climate fingerprinting is that most of the observed changes studied to date are consistent with each other, and are also consistent with our scientific understanding of how the climate system would be expected to respond to the increase in heat-trapping gases resulting from human activities.[9]

 

[westwall]

Climate model, climate model, climate model, climate model. Ever notice how you science deniers always confuse climate models with actual data?

Have you further noticed that when the actual data refutes your models you falsify the data to support your models?

And you claim to understand science

 

[jc456]

Detection vs Attribution

Detection and attribution of climate signals, as well as its common-sense meaning, has a more precise definition within the climate change literature, as expressed by the IPCC.[17]

Detection of a signal requires demonstrating that an observed change is statistically significantly different from that which can be explained by natural internal variability.

Attribution requires demonstrating that a signal is:

unlikely to be due entirely to internal variability;
consistent with the estimated responses to the given combination of anthropogenic and natural forcing
not consistent with alternative, physically plausible explanations of recent climate change that exclude important elements of the given combination of forcings.

Detection does not imply attribution, and is easier to show than attribution. Unequivocal attribution would require controlled experiments with multiple copies of the climate system, which is not possible. Therefore, attribution, as described above, can only be done within some margin of error. For example, the IPCC's Fourth Assessment Report says "it is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750," where "extremely likely" indicates a probability greater than 95%.[1]

So.....you have no proof. tsk, tsk, and yet you believe in mumbo jumbo when the data doesn't support the liars. Now that is denying.

That is an epic fail!

 

[Kosh]

The AGW cult continues to prove that the true deniers are them as they deny real science.

 

[Crick]

This set of graphs shows the estimated contribution of various natural and human factors to changes in global mean temperature between 1889-2006.[41] Estimated contributions are based on multivariate analysis rather than model simulations.[42] The graphs show that human influence on climate has eclipsed the magnitude of natural temperature changes over the past 120 years.[43] Natural influences on temperature-El Niño, solar variability, and volcanic aerosols-have varied approximately plus and minus 0.2 °C (0.4 °F), (averaging to about zero), while human influences have contributed roughly 0.8 °C (1 °F) of warming since 1889.[43]

Frequency of occurrence (vertical axis) of local June-July-August temperature anomalies (relative to 1951-1980 mean) for Northern Hemisphere land in units of local standard deviation (horizontal axis).[46] According to Hansen et al. (2012),[46] the distribution of anomalies has shifted to the right as a consequence of global warming, meaning that unusually hot summers have become more common. This is analogous to the rolling of a dice: cool summers now cover only half of one side of a six-sided die, white covers one side, red covers four sides, and an extremely hot (red-brown) anomaly covers half of one side.[46]

Detection and attribution studies

In 1996, in a paper in Nature titled "A search for human influences on the thermal structure of the atmosphere", Benjamin D. Santer et al. wrote: "The observed spatial patterns of temperature change in the free atmosphere from 1963 to 1987 are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability."
A 2002 paper in the Journal of Geophysical Research says "Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming."[58][59]
A 2005 review of detection and attribution studies by the International Ad Hoc Detection and Attribution Group[60] found that "natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that 'most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.'"
Barnett and colleagues (2005) say that the observed warming of the oceans "cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models," concluding that "it is of human origin, a conclusion robust to observational sampling and model differences"[61]
Two papers in the journal Science in August 2005[62][63] resolve the problem, evident at the time of the TAR, of tropospheric temperature trends (see also the section on "fingerprint" studies) . The UAH version of the record contained errors, and there is evidence of spurious cooling trends in the radiosonde record, particularly in the tropics. See satellite temperature measurements for details; and the 2006 US CCSP report.[64]
Multiple independent reconstructions of the temperature record of the past 1000 years confirm that the late 20th century is probably the warmest period in that time (see the preceding section -details on attribution).

 

[Crick]

Climate model, climate model, climate model, climate model. Ever notice how you science deniers always confuse climate models with actual data?

Climate model, climate model, climate model. Ever notice how science deniers pull out this mantra every time they hear the term and think they can reject all model work without providing the slightest hint of evidence that anything is wrong with the models under question? Besides, if you'll actually take the time to read the articles, you'll find a great deal of real measurements being discussed.

Have you further noticed that when the actual data refutes your models you falsify the data to support your models?

No, we haven't. Because it has not. You really ought to read the article before making asinine pronouncements like this.

And you claim to understand science

I obviously understand it a damn sight better than you.

 

[Crick]

Reviews of scientific opinion

An essay in Science surveyed 928 abstracts related to climate change, and concluded that most journal reports accepted the consensus.[65] This is discussed further in scientific opinion on climate change.

A 2010 paper in the Proceedings of the National Academy of Sciences found that among a pool of roughly 1,000 researchers who work directly on climate issues and publish the most frequently on the subject, 97% agree that anthropogenic climate change is happening.[66]

A 2011 paper from George Mason University published in the International Journal of Public Opinion Research, "The Structure of Scientific Opinion on Climate Change," collected the opinions of scientists in the earth, space, atmospheric, oceanic or hydrological sciences.[67] The 489 survey respondents-representing nearly half of all those eligible according to the survey's specific standards - work in academia, government, and industry, and are members of prominent professional organizations.[67] The study found that 97% of the 489 scientists surveyed agreed that that global temperatures have risen over the past century.[67] Moreover, 84% agreed that "human-induced greenhouse warming" is now occurring."[67] Only 5% disagreed with the idea that human activity is a significant cause of global warming.[67]

As described above, a small minority of scientists do disagree with the consensus: see list of scientists opposing global warming consensus. For example Willie Soon and Richard Lindzen[68] say that there is insufficient proof for anthropogenic attribution. Generally this position requires new physical mechanisms to explain the observed warming.[69]
******************************************
Said mechanisms still sorely lacking.

 

[westwall]

This set of graphs shows the estimated contribution of various natural and human factors to changes in global mean temperature between 1889-2006.[41] Estimated contributions are based on multivariate analysis rather than model simulations.[42] The graphs show that human influence on climate has eclipsed the magnitude of natural temperature changes over the past 120 years.[43] Natural influences on temperature-El Niño, solar variability, and volcanic aerosols-have varied approximately plus and minus 0.2 °C (0.4 °F), (averaging to about zero), while human influences have contributed roughly 0.8 °C (1 °F) of warming since 1889.[43]

Frequency of occurrence (vertical axis) of local June-July-August temperature anomalies (relative to 1951-1980 mean) for Northern Hemisphere land in units of local standard deviation (horizontal axis).[46] According to Hansen et al. (2012),[46] the distribution of anomalies has shifted to the right as a consequence of global warming, meaning that unusually hot summers have become more common. This is analogous to the rolling of a dice: cool summers now cover only half of one side of a six-sided die, white covers one side, red covers four sides, and an extremely hot (red-brown) anomaly covers half of one side.[46]

Detection and attribution studies

In 1996, in a paper in Nature titled "A search for human influences on the thermal structure of the atmosphere", Benjamin D. Santer et al. wrote: "The observed spatial patterns of temperature change in the free atmosphere from 1963 to 1987 are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability."
A 2002 paper in the Journal of Geophysical Research says "Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming."[58][59]
A 2005 review of detection and attribution studies by the International Ad Hoc Detection and Attribution Group[60] found that "natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that 'most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.'"
Barnett and colleagues (2005) say that the observed warming of the oceans "cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models," concluding that "it is of human origin, a conclusion robust to observational sampling and model differences"[61]
Two papers in the journal Science in August 2005[62][63] resolve the problem, evident at the time of the TAR, of tropospheric temperature trends (see also the section on "fingerprint" studies) . The UAH version of the record contained errors, and there is evidence of spurious cooling trends in the radiosonde record, particularly in the tropics. See satellite temperature measurements for details; and the 2006 US CCSP report.[64]
Multiple independent reconstructions of the temperature record of the past 1000 years confirm that the late 20th century is probably the warmest period in that time (see the preceding section -details on attribution).

They're doing multivariate analysis of COMPUTER MODELS! Once again you confound facts with models.

 

[Kosh]

Earth's temperature has not risen significantly since 1998 and has cooled by 0.5oC since early 2007. Even the United Nations has quietly admitted this. This is completely contrary to the CO2 caused global warming theory, which states that the earth's temperature should be quickly rising because atmospheric CO2 is rising quickly. The UN and those who support the CO2 warming theory claim that the cooling is just a temporary glitch and earth's temperature will began to rise again in a year or two. However, as explained, a majority of scientists now believe that we are in for a 15 to 35 year cooling cycle that has nothing to do with CO2 and everything to do with solar activity and temperature oscillations of the oceans.

 

[SSDD]

I wonder how many of these warmer idiots will suicide out of sheer despair when the hoax finally comes tumbling down?

 

[westwall]

I wonder how many of these warmer idiots will suicide out of sheer despair when the hoax finally comes tumbling down?

Oh, I suspect none of them. They'll just move on to the next con job. That's what they do.

 

[SSDD]

Many of them seem to have bet all their emotional chips on this one...the level of shrillness, and desperation has gone way beyond any of the past envirowacko causes of the past half a century or so.

 

[Crick]

This was the post immediately above the exclamation, "climate model, climate model, climate model"

Detection and attribution studies

In 1996, in a paper in Nature titled "A search for human influences on the thermal structure of the atmosphere", Benjamin D. Santer et al. wrote: "The observed spatial patterns of temperature change in the free atmosphere from 1963 to 1987 [measurements] are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability."
A 2002 paper in the Journal of Geophysical Research says "Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming."[58][59]
A 2005 review of detection and attribution studies by the International Ad Hoc Detection and Attribution Group[60] found that "natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century[measurements], and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that 'most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.'"
Barnett and colleagues (2005) say that the observed warming of the oceans [measurements] "cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models," concluding that "it is of human origin, a conclusion robust to observational sampling and model differences"[61]
Two papers in the journal Science in August 2005[62][63] resolve the problem, evident at the time of the TAR, of tropospheric temperature trends (see also the section on "fingerprint" studies) . The UAH version of the record contained errors, and there is evidence of spurious cooling trends in the radiosonde record[measurements - found to be flawed], particularly in the tropics. See satellite temperature measurements for details [measurements]; and the 2006 US CCSP report.[64]
Multiple independent reconstructions of the temperature record of the past 1000 years confirm that the late 20th century is probably the warmest period in that time (see the preceding section -details on attribution).

 

[Kosh]

Before the Little Ice Age, research studies have shown that there were two major warming periods; the Medieval Climate Optimum and the Holocene Optimum when it was 1.5 to nearly 3 degrees C warmer than it is today. The Vikings colonized Greenland during the Medieval Climate Optimum when they could actually grow crops on Greenland. By the 1400s Greenland had become so cold that these colonies had to be abandoned

 

[Crick]

Many of them seem to have bet all their emotional chips on this one...the level of shrillness, and desperation has gone way beyond any of the past envirowacko causes of the past half a century or so.

The level of shrillness? The only thing I've put up here so far is extracts from Wikipedia articles. You're the ones with all the personal insults.

 

[SSDD]

Many of them seem to have bet all their emotional chips on this one...the level of shrillness, and desperation has gone way beyond any of the past envirowacko causes of the past half a century or so.

The level of shrillness? The only thing I've put up here so far is extracts from Wikipedia articles. You're the ones with all the personal insults.

Once again the conversation goes right over your head. Your response does bolster my point though. ...thanks.

 

[mamooth]

Deniers, enjoy your descent into senility and substance abuse, which we can all see is well underway.

And while you're drooling on to your bibs, the science will be leaving you ever farther behind. We can't even see you in the rear view mirror any longer.

 

[Kosh]

It is often reported that the temperature of the earth is higher the past 20 years than it has ever been in history. This is simply not true, nor has it ever been. Hundreds of research studies using ice cores, pollen sedimentation, tree rings, etc. have shown that there were dozens of periods in the past 11,000 years (the Holocene period) that earth's temperature was warmer than it is today. Earth's temperature was very much warmer at least four times during the current interglacial period.

 

[Crick]

Many of them seem to have bet all their emotional chips on this one...the level of shrillness, and desperation has gone way beyond any of the past envirowacko causes of the past half a century or so.

The level of shrillness? The only thing I've put up here so far is extracts from Wikipedia articles. You're the ones with all the personal insults.

Once again the conversation goes right over your head. Your response does bolster my point though. ...thanks.

The total denier input into this thread consists of nothing but insults and unsupported opinion. My input has consisted entirely of discussions of peer reviewed scientific studies. Where do you see "shrillness and desperation" in my posts?

Asshole.