[Tim the Plumber (OP)]

I wish to ask those who consider that there is any significant threat from climate change due to human activity what it would take for you to consider the hypothesis failed? That is what would it take for there to be nothing to worry about from it?

Given it has not caused any trouble so far there must be the posibility that the whole thing is a scare over nothing so what would it take for you to come to this conclusion?

[alancalverd]

I can't speak for the believers, but I would be less unimpressed by the hypothesis if we had a sensible prediction of what would happen if we reduced CO2 emissions, and we did so, and it came true. But then I'm just a bloody scientist - who cares what I think when there are journalistic and political careers, headline-making conference dinners, and serious money at stake?

Successive governments having destroyed the UK coal industry in order to get re-elected, it is absolutely essential for the population to continue to believe that coal burning is a Bad Thing.

Successive governments having given wads of your cash to windmill and solar panel manufacturers, it is absolutely essential for the population to continue to believe that unreliable sources of electricity are a Good Thing.

The blessed European Union having decreed that recyclable filament lamps must be replaced by toxic fluorescents or Chinese LEDs (and more central heating), it is absolutely essential that the population continues to believe that switching on a filament lamp is tantamount to nailing the Baby Jesus to the Cross. 

Successive governments having privatised railways and water supply and encouraged speculative jerrybuilding on flood plains, it is absolutely essential that the population continue to believe that flooding, chaos, drowned cattle, rotten crops and general disruption are all your fault for daring to drive a car (Ministerial Jaguars don't count).

And it isn't just a problem for British politicians. Populations in less hospitable climates having been encouraged to (or at least not discouraged from) breed themselves into unsustainabilty, it is essential that they continue to believe that that the lack of food and water is due to decadent Westerners flying to Australia.

If the bogeyman of AGW didn't exist, politicians would have to blame someone else for the consequences of political corruption and incompetence, or face the threat of revolution and redistribution of power to those with the competence and honesty to use it properly - what politicians call anarchy.

[Tim the Plumber (OP)]

To Bored Chemist,

It would be really nice to know what it would take in your case.

[Bored chemist]

To Bored Chemist,

It would be really nice to know what it would take in your case.

As I have said before, The first step would be to explain how adding CO2 didn't cause warming.
It's a greenhouse gas.
You would need to explain how it somehow didn't raise the temperature.

Nobody yet has got close to doing that.

BTW, Alan, Maggie destroyed the mining industry because the unions were a strong voice opposing hers. It had nothing to do with climate change.

Also, speaking out in favour of a century old technology that's 97% inefficient is "interesting".
If you find that fluorescent lights are toxic, I suggest that you stop eating them.

[alancalverd]

BTW, Alan, Maggie destroyed the mining industry because the unions were a strong voice opposing hers. It had nothing to do with climate change.

We know that, but the trick is to get the population to believe that what she did was a Good Thing. The UK now sits on about 200 years' supply of coal that cannot be mined safely or economically, ever. If were was no mitigating factor, the Conservative party would be unelectable, and we can't have that, can we? 

Also, speaking out in favour of a century old technology that's 97% inefficient is "interesting".

I used to heat my kitchen with 500W of tungsten lighting. When I replaced the bulbs with CFLs, I had to install bigger radiators to make up the deficit. Trouble is that the radiators heated the walls and windows, whereas the lamps used to heat the people, so the net efficiency decreased. I've no objection to CFL and LED lighting where heating is undesirable and long life is essential, but it would be nice to have an efficient ceiling-mounted radiant heater again!   

Apropos your main point, however, the earth's climate is such a complex system that, even though it is scientifically obvious that CO2 is not a significant driver, it would be very difficult to produce a realistic and predictive model based on water, the major greenhouse gas.  The only way to convince anyone who isn't impressed by simple physics (i.e. most people) is to wait until the temperature starts to decrease whilst CO2 remains constant or increases. By that time, however, I'm sure everyone will have lost interest and a bigger bogeyman will be foisted upon the taxpayer.. It's worth remembering that income tax, believed by most people to be as essential as DNA, was actually introduced as a temporary measure to pay for the Napoleonic Wars. How short the public memory....

[puppypower]

One way to refute man made climate change is to explain how the magic trick works. If you went to a magic show and the audience saw someone levitate, it will be hard to convince people it did not happen, unless you can show how the trick works.

There are several aspects to the man made climate change magic trick. One aspect is connected to hyped fear. For example, when an airliner crashes (beyond terrorism), there will be a lot of media hype and endless expert analysis. After listening to this for several days, many people begin to assume all air travel is at risk. Politicians will cater to the fear insisting something needs to be done, industry wide. The induced fear and hype, reinforce by the actions of leadership, will cloud judgment. This fear is the house lights being dimmed for the magic trick. All the doom and gloom predictions, connected to man made global warming, that never panned out was the house lights dimming. It did not matter if this happened or not, the goal was the fear. Those who got the fear bug, will not care if the bogeyman did not show, since he is out there.

Another aspect of the magic trick is connected to semantics. When they say this is the warmest summer on record, science only has good weather data for about 150 years, tops, even though the earth is 6 billion years old. Yet the term, on record, is often interpreted by the fearful, to mean the entire life of the earth. Nobody who performs this magic trick will ever clarify this.

This distraction blends into the next aspect of the illusion. We generate more weather data, today, than any time in history of weather data collection. More data makes it look like more is happening. From a satellite, you can see weather in remote areas where data was never collected. This counts as manmade change, since nothing there could be substantiated, to prove otherwise.

If we needed to look at the weather from 200 years ago, there is little if any direct data to use. Even if this was the worse in 500 years, it is still not the worse on record, since officials records are 150 years old. Due too the scarcity of the hard direction data, one may need to rely on indirect data, like tree rings to give us a clue of what happened. This can tell us the annual averages, but you can't see day to day like we record today. The result is there is more climate change today, based on a hard data.

Here is an experiment we can do in schools. This is the magic trick. We will have a group of students observe and record, with their cell phone cameras, any bird or squirrel they see, during one month of time. When all the data is compiled, we will tell them there are more birds and squirrels in that area, now, that in any anytime in history.

Technically, the students will have recorded more hard data than any skeptic can produce, for any other time in history, for that area. The claim of more birds and squirrels, although unsubstantiated and probably not true, will be hard to disprove, especially since anyone who denies my claim, will not be able to provide as much hard evidence as the students. We then make fun of the skeptics so they don't spoil the trick.

To help my claim along, I will use fear to dim the house lights. I tell them that bird and squirrel droppings can cause disease. This is the distraction needed to get others to fixate on birds and droppings so thy start to observe and see more than they ever noticed before. The fear will require something be done, with the school now making a big deal about cleaning the sidewalks. This will reinforce the fear, due to remediation being employed.
 

.

[evan_au]

Given it has not caused any trouble so far

I think your question is based on a false premise.
- In our part of the world, coral bleaching is a problem.
- In the Champagne valley, their climate has moved to the south of England (but they won't tell you that).
- There are a number of species that are being pushed to extinction by being pushed to the edge of their habitat.
- There have been some rather destructive hurricanes in coastal USA.

None of these individual events can be blamed with 100% certainty on human-induced climate change.
- But if human-induced climate change increases the severity of hurricanes by 10%, by the time there are 10 hurricanes, you could say that one of them is caused by humans.
- The El Nino cycle contributes to coral bleaching - but the bleaching is worse by 1K due to the action of humans
- Habitat destruction and fragmentation contributes to extinctions. But it is climate change that pushes the species out of the end of their nature reserve

[smart]

The fiddling of temperature data on a global scale through climate engineering is a strong evidence that climate change is a hoax. The official narratives of climate change may be manipulated to promote the pseudoscientific model of global warming.

Thus faking data by doing solar radiation management (chemtrails) could have the opposite effect on global temperature levels and may contribute to ozone depletion in the atmosphere. Ozone depletion and climate change are deeply interconnected.

http://www.telegraph.co.uk/news/earth/environment/globalwarming/11395516/The-fiddling-with-temperature-data-is-the-biggest-science-scandal-ever.html

http://geoarchitektur.blogspot.ca/p/faking-data-for-geoengineering.html

https://en.wikipedia.org/wiki/Ozone_depletion_and_climate_change

[Tim the Plumber (OP)]

To Bored Chemist,

It would be really nice to know what it would take in your case.

As I have said before, The first step would be to explain how adding CO2 didn't cause warming.
It's a greenhouse gas.
You would need to explain how it somehow didn't raise the temperature.

Nobody yet has got close to doing that.

BTW, Alan, Maggie destroyed the mining industry because the unions were a strong voice opposing hers. It had nothing to do with climate change.

Also, speaking out in favour of a century old technology that's 97% inefficient is "interesting".
If you find that fluorescent lights are toxic, I suggest that you stop eating them.

So data from the world showing that it was not warming would not do it.

If it got colder would that do it?

If the IPCC's predictions were narrowed down to the low end of the range at which there is almost no cause for concearn would you then think there was nothing to worry about?

You see I am not trying to disprove the science of IR absorption I just want to know what level of warming is OK and how you would get to that position.

[alancalverd]

I think your question is based on a false premise.
- In our part of the world, coral bleaching is a problem.

For the coral, certainly. But the Great Barrier Reef is itself a product of geologically recent climate change!

- In the Champagne valley, their climate has moved to the south of England (but they won't tell you that).

Actually, moved back to southern England, where it was in Roman times and up to the 11th century. I suppose you could blame the bloody Romans and their excessive use of hot baths and central heating, but somehow or other the Ancient Britons managed to survive for thousands of years, clad only in woad and paganism. They didn't even bother to put roofs and walls on Stonehenge.

- There are a number of species that are being pushed to extinction by being pushed to the edge of their habitat.

'twas ever this, quoth the diplodocus. And you can't blame humans for that.

- There have been some rather destructive hurricanes in coastal USA.

though fewer Grade 5s have been recorded pretty much each year since the 1850s. The damage caused has increased, because more people now live, in less robust houses, and with more expensive cars and boats, on the south east coast. And Katrina wouldn't have been a major problem if they hadn't drained the swamps to build houses on the outskirts of New Orleans.

[Blame]

Doesn't much matter really. Just as long as its attached to sufficiently large backhander from the oil industry. 

But if you are serious then another source for all that CO2 or a convincing explanation for Siberia defrosting without our help.

You sure ain't going to convince me that the climate hasn't changed.

but why bother? the smart move is to give up on "its not our fault" in favor of "its too late/too expensive to fix".

[alancalverd]

Curious how True Believers keep asserting that skeptics deny the obvious. But the essence of faith is, of course, acceptance of a hypothesis in the face of the facts.

Climate is changing - fact. Climate always has changed - fact. Most of these changes occurred long before industrialisation - fact. Which makes the hypothesis of significant anthropogenically-driven change just a teeny bit unlikely.

Nevertheless we press on and create models based on recent data. The only reliable global data is from 1970 onwards though we have some reasonably good urban data from 1930. Then it turns out that the only way we can make this recent historic data fit the anthropogenic model is to "correct" the data, and even then, the model isn't usefully predictive - fact.

So we make broad-brush statements about "never in recorded history" and suchlike. Until we find 500-year-old bromeliads under a retreating glacier. Unless you accept that they were put there by the Devil to confuse unbelievers, the only rational explanation is that the glacier wasn't there 500 years ago - fact. 

All of which suggests that climate change is real (which we knew already) but probably not significantly anthropogenic. That's science, not faith.

[agyejy]

Climate is changing - fact. Climate always has changed - fact. Most of these changes occurred long before industrialisation - fact. Which makes the hypothesis of significant anthropogenically-driven change just a teeny bit unlikely.

That's not even remotely how logical inference works nor does it address the very real differences between the changes predicted for natural climatic process vs the changes we are currently seeing. One of the clearest signs of the greenhouse effect is that the upper levels of the atmosphere are cooling as the atmosphere near the surface warms. The only thing that can account for this is increased heat retention via greenhouse gasses and the greenhouse gas that is most clearly increasing is CO2 and the only new source of CO2 is humans. The fact that climate has changed in the past in no way counters that argument not the least of which because it complete ignores the differences in the changes we are seeing now from natural changes.

http://www.skepticalscience.com/climate-change-little-ice-age-medieval-warm-period-intermediate.htm <- A more detailed argument than I have presented.

http://www.skepticalscience.com/its-not-us-advanced.htm <- Here is a fuller accounting of the various different pieces of evidence that place the blame on us.

Nevertheless we press on and create models based on recent data. The only reliable global data is from 1970 onwards though we have some reasonably good urban data from 1930. Then it turns out that the only way we can make this recent historic data fit the anthropogenic model is to "correct" the data, and even then, the model isn't usefully predictive - fact.

You point about the data simply isn't true: http://www.skepticalscience.com/surface-temperature-measurements-advanced.htm
A blind review of climate science claims from both opponents and proponents has been conducted using experts in statistical analysis: https://www.researchgate.net/publication/303028762_A_blind_expert_test_of_contrarian_claims_about_climate_data

It was found that the claims of mainstream climate science are credibly supported by the available data while statements to the contrary were found to be misleading. I emphasis this study was blind and avoided bias by not letting the judging experts know exactly to what the supporting data pertained.

All of which suggests that climate change is real (which we knew already) but probably not significantly anthropogenic. That's science, not faith.

Again nothing above actually address the very real evidence and arguments for human induced climatic change. Since it bears repeating:

http://www.skepticalscience.com/its-not-us-advanced.htm <- Here is a fuller accounting of the various different pieces of evidence that place the blame on us.

I've actually run into the character limit so I'm actually going to make this a two parter.

[agyejy]

Continued from above:

Since past experience here as indicated a reluctance to actually follow a link in order to read the evidence I'm going to quote the entire article here. I apologize for the length but I feel it is necessary due to the refusal of people to follow a link disproving their statements only to repeat those statements later.

-------------------------------------------------------------
Surface Temperature Change

Back in 1988, NASA's James Hansen made some of the first projections of future global warming with a global climate model (Hansen 1988). He created 3 scenarios which he called Scenarios A, B, and C which used various possible future greenhouse gas emissions levels. Scenario A used a model with accelerating greenhouse gas emissions, Scenario B had linearly increasing emissions, and Scenario C had emissions leveling off after the year 2000. None of these models ended up matching greenhouse gas emissions exactly right, but the radiative forcing (energy imbalance) in Scenario B was closest, too high by about 10% as of 2009. Additionally, the climate sensitivity in Hansen's 1988 model (4.2°C global warming for a doubling of atmospheric CO2) was a bit higher than today's best estimate (3°C warming for CO2 doubling).

Hansen's Scenario B projected a global warming trend from 1984-2009 of 0.26°C per decade. The actual trend as measured by surface temperature stations over that period was about 0.2°C per decade. When corrected for the 10% smaller radiative forcing than Scenario B and the higher climate sensitivity in Hansen's models, his study projected the global warming over the ensuing 25 years almost perfectly.

Meehl et al. (2004) took a different approach. Instead of projecting future surface temperature change, they used climate models to attempt to attribute past temperature changes in a method known as 'hindcasting' (as opposed to forecasting). In their study, Meehl et al. show that natural forcings cannot account for the increase in global temperatures in the second half of the 20th century, and that models using both natural and anthropogenic forcings model the temperature change over the 20th century most accurately.

"The late-twentieth-century warming can only be reproduced in the model with anthropogenic forcing (mainly GHGs), while the early twentieth-century warming is mainly caused by natural forcing in the model (mainly solar)."


Figure 1: Anthropogenic plus natural vs. just natural radiative forcing temperature change vs. observed global surface temperature increase (Meehl 2004)

A number of studies using a variety of different statistical and physical approaches have, like Meehl 2004, estimated the human and natural contributions to global warming.  They universally find that humans are the dominant cause of the observed global warming over the past 150 years, 100 years, 50 years, 25 years, etc.  In fact, many conclude that natural effects have actually been in the cooling direction in recent decades (Figure 2).


Figure 2: Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J12, pink).

Stott et al. (2003) took yet another approach, examining surface temperature changes region-by-region across the planet and comparing them to how climate models predicted they should have changed. Stott found that regional temperature changes could also be traced back to anthropogenic global warming.

"The causes of twentieth century temperature change in six separate land areas of the Earth have been determined by carrying out a series of optimal detection analyses. The warming effects of increasing greenhouse gas concentrations have been detected in all the regions examined, including North America and Europe….Our results show significant anthropogenic warming trends in all the continental regions analyzed. In all these regions, greenhouse gases are estimated to have caused generally increasing warming as the century progressed, balanced to a greater or lesser degree, depending on the region, by cooling from sulfate aerosols in the middle of the century."



More warming at night than day

Climate models predict that as a consequence of anthropogenic global warming, the planet should warm more at night than during the day. This is also known as a decreasing diurnal temperature range (DTR – the difference between minimum and maximum daily temperature). Braganza et al. (2004) investigated the changes in DTR over the past 50 years and concluded as follows:

"Observed DTR over land shows a large negative trend of ~0.4°C over the last 50 years that is very unlikely to have occurred due to internal variability. This trend is due to larger increases in minimum temperatures (~0.9°C) than maximum temperatures (~0.6°C) over the same period. Analysis of trends in DTR over the last century from five coupled climate models shows that simulated trends in DTR due to anthropogenic forcing are much smaller than observed. This difference is attributable to larger than observed changes in maximum temperatures in four of the five models analysed here, a result consistent with previous modelling studies."

Essentially Braganza et al. found that that while DTR is decreasing as expected by climate models, it’s decreasing more than they predicted because daytime temperatures are increasing less than they predict, possibly because the models omit changes in the Earth’s reflectivity from factors like cloudcover and land use change. Here you can see the observed changes in maximum, minimum, mean global temperature, and DTR vs. predictions by the four climate models used in the study.


Figure 4: Observed vs. modeled temperature trends (Braganza 2004)

Stratospheric Temperature Change

As the lower atmosphere warms due to an enhanced greenhouse effect, the upper atmosphere is expected to cool as a consequence. The simple way to think about this is that greenhouse gases are trapping heat in the lower atmosphere. Since less heat is released into the upper atmosphere (starting with the stratosphere), it cools.

Jones et al. (2003) investigated the changes in temperature over the past 4 decades at both the near surface (troposphere) and stratosphere layers, and compare them to changes predicted by a coupled atmosphere/ocean general circulation model, HadCM3. They concluded as follows.

"Our results strengthen the case for an anthropogenic influence on climate. Unlike previous studies we attribute observed decadal-mean temperature changes both to anthropogenic emissions, and changes in stratospheric volcanic aerosols. The temperature response to change in solar irradiance is also detected but with a lower confidence than the other forcings."

Tropopause Height

The tropopause is the atmospheric boundary between the troposphere and the stratosphere. Observations indicate that the tropopause height has increased several hundred meters over the past 3 decades. Santer et al. (2003) investigated the causes of this change and concluded as follows.

"Comparable increases are evident in climate model experiments. The latter show that human-induced changes in ozone and well-mixed greenhouse gases account for ~80% of the simulated rise in tropopause height over 1979–1999. Their primary contributions are through cooling of the stratosphere (caused by ozone) and warming of the troposphere (caused by well-mixed greenhouse gases). A model predicted fingerprint of tropopause height changes is statistically detectable in two different observational (“reanalysis”) data sets. This positive detection result allows us to attribute overall tropopause height changes to a combination of anthropogenic and natural external forcings, with the anthropogenic component predominating."


Figure 5: Changes in temperature and tropopause height in response to various radiative forcings (Santer 2003)

Upper Atmosphere Temperature Change

The layers above the stratosphere are expected to cool as a result of global warming as well, for similar reasons (less heat reaching higher levels as it’s trapped in the lower atmosphere). Jarvis et al. (1998) investigated changes in the thermosphere and ionosphere in 1998 and concluded as follows.

"The estimated long-term decrease in altitude is of a similar order of magnitude to that which has been predicted to result in the thermosphere from anthropogenic change related to greenhouse gases."
Laštovička et al. (2006) arrived at a similar conclusion.

"The upper atmosphere is generally cooling and contracting, and related changes in chemical composition are affecting the ionosphere. The dominant driver of these trends is increasing greenhouse forcing, although there may be contributions from anthropogenic changes of the ozone layer and long-term increase of geomagnetic activity throughout the 20th century. Thus, the anthropogenic emissions of greenhouse gases influence the atmosphere at nearly all altitudes between ground and space, affecting not only life on the surface but also the space-based technological systems on which we increasingly rely."


Figure 6: Atmospheric temperature and Ionospheric electron density vs. Altitude (Laštovička 2006)

Ocean Heat Content

Ocean heat content has increased significantly over the past 40 years. In fact, approximately 84% of the total heating of the Earth system over that period has gone into warming the oceans. Barnett et al. (2005) investigated the cause of this warming signal, and concluded as follows.

"[the increase in ocean heat content] cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change."


Figure 7: Modeled vs. Observed Ocean Temperature Changes

Sea Level Pressure

Gillett et al. (2003) compared observed changes in sea level pressure with those predicted by four coupled ocean–atmosphere climate models and concluded as follows.

"Here we detect an influence of anthropogenic greenhouse gases and sulphate aerosols in observations of winter sea-level pressure (December to February), using combined simulations from four climate models. We find increases in sea-level pressure over the subtropical North Atlantic Ocean, southern Europe and North Africa, and decreases in the polar regions and the North Pacific Ocean, in response to human influence….Overall, we find that anthropogenic greenhouse gases and sulphate aerosols have had a detectable influence on sea-level pressure over the second half of the twentieth century: this represents evidence of human influence on climate independent of measurements of temperature change."

Precipitation

Zhang et al. (2007) showed that models using natural + anthropogenic forcings do a much better job of matching observed precipitation trends than either natural or anthropogenic alone. The correlation with natural forcings alone is extremely weak - only 0.02. With anthropogenic alone is 0.69, and with both combined is 0.83 over the past 75 years.

"We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation"

Infrared Radiation

Increase in downward longwave radiation

Anthropogenic global warming is caused by an increase in the amount of downward longwave infrared radiation coming from greenhouse gases in the atmosphere. Philipona et al. (2004) measured the changes and trends of radiative fluxes at the surface and their relation to greenhouse gas increases and temperature and humidity changes measured from 1995 to 2002 at eight stations of the Alpine Surface Radiation Budget (ASRB) network. They concluded as follows.

"The resulting uniform increase of longwave downward radiation manifests radiative forcing that is induced by greenhouse gas concentrations and water vapor feedback, and proves the "theory" of greenhouse warming with direct observations."
Evans et al. (2006) took it a step further, performing an analysis of high resolution specral data which allowed them to quantitatively attribute the increase in downward radiation to each of several greenhouse gases. The study went as far as to conclude,

"This experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming."

Decrease in upward longwave radiation

As the concentration of greenhouse gases in the atmosphere increases, we expect to see less infrared radiation escaping at the top of the atmosphere. Satellite observations have confirmed that the decrease in upward longwave radiation matches well with model predictions, including in Harries 2001, Griggs 2004, and Chen 2007, the latter of which concluded:

"Changing spectral signatures in CH4, CO2, and H2O are observed, with the difference signal in the CO2 matching well between observations and modelled spectra."


Figure 8: Increased greenhouse effect from 1970 to 2006. Black line is satellite observations. Red line is modeled results (Chen 2007)

Increased top of the atmosphere energy imbalance

This increase in downward and decrease in upward infrared radiation is expected to create an enery imbalance. Trenberth et al. (2009) used satellite data to measure the Earth's energy balance at the top of the atmosphere (TOA) and found that the net imbalance was 0.9 Watts per square meter. (Wm-2) This figure is consistent with the calculations in Hansen et al. 2005 using ocean heat data.

"The predicted energy imbalance due to increasing greenhouse gases has grown to 0.85 ± 0.15 W/m2"


Figure 9: TOA Radiation (Trenberth 2009)

Murphy et al. (2009) obtained a similar result.

"About 20% of the integrated positive forcing by greenhouse gases and solar radiation since 1950 has been radiated to space. Only about 10% of the positive forcing (about 1/3 of the net forcing) has gone into heating the Earth, almost all into the oceans. About 20% of the positive forcing has been balanced by volcanic aerosols, and the remaining 50% is mainly attributable to tropospheric aerosols. After accounting for the measured terms, the residual forcing between 1970 and 2000 due to direct and indirect forcing by aerosols as well as semidirect forcing from greenhouse gases and any unknown mechanism can be estimated as 1.1 ± 0.4 Wm-2."


Figure 10: Cumulative energy budget for the Earth since 1950 (Murphy 2009)

This is an impressively wide variety of global and regional climate change observations strongly matching the changes predicted by climate models and providing clear fingerprints of human-caused climate change.
-------------------------------------------------------------

Clearly there is a lot of evidence supporting human caused global climate change and much of that evidence is actually independent of surface temperature records.

[alancalverd]

One of the clearest signs of the greenhouse effect is that the upper levels of the atmosphere are cooling as the atmosphere near the surface warms.

Which of course is entirely different from the measurements you made 400,000 years ago. Or even 500 years ago.

[agyejy]

Which of course is entirely different from the measurements you made 400,000 years ago. Or even 500 years ago.

Those measurements are unnecessary. The Earth and its atmosphere are physical systems that obey the rules of physics. The atmosphere may be a chaotic system but we've been modeling chaotic systems with high degrees of precision for awhile now. However, you don't even need a model to understand that the only reason for the surface atmosphere to increase in temperature while the upper atmosphere cools is the greenhouse effect. There is literally no other physical process that could cause that and the only new significant source of greenhouse gasses is human activity. Beyond that as the article I quoted pointed out there is a veritable mountain of other evidence that is not temperature related that proves the current climate change we are seeing is caused by humans.

Some other particularly important bits from the article I quoted (you really should read it) are the direct measurements of increased downward infrared radiation in the lower atmosphere and decreased upward infrared radiation from the upper atmosphere leading directly to a measurable energy imbalance in the upper atmosphere indicating a net increase in thermal energy trapped by the Earth. In short direct measurements of the greenhouse effect in action and given that the only new significant source of greenhouse gasses is human activity the implications are inescapable.

[alancalverd]

The atmosphere may be a chaotic system but we've been modeling chaotic systems with high degrees of precision for awhile now.

Except for the atmosphere, where IPCC has admitted that the behavior of the water system is too complex to model, and no model has yet had any useful predictive value.

Hansen's Scenario B projected a global warming trend from 1984-2009 of 0.26°C per decade. The actual trend as measured by surface temperature stations over that period was about 0.2°C per decade.

If I made a 30% error in my work, people would die and I would lose my job. But who cares about 30% when politics is involved?

When corrected for the 10% smaller radiative forcing than Scenario B and the higher climate sensitivity in Hansen's models, his study projected the global warming over the ensuing 25 years almost perfectly.

"Prediction is very difficult, especially about the future" Nobody doubts Mr Berra's famous truism. Prediction about the past, however, is ridiculously easy. If I had enough data, I could tell you what you had for breakfast yesterday. But would that convince anyone that I had the authority to tell you what to eat tomorrow? 

[agyejy]

Except for the atmosphere, where IPCC has admitted that the behavior of the water system is too complex to model, and no model has yet had any useful predictive value.

Surely you can point me to the exact document from the IPCC that says this.

If I made a 30% error in my work, people would die and I would lose my job. But who cares about 30% when politics is involved?

There is obviously a very big difference between what you do and statistical modeling of chaotic processes. For example, if you prove to a stock broker that you can predict the price of a stock to within a 30% margin or error that stock broker would basically throw money at you and you'd both get rich. What is important about climate modeling is not 100% accuracy (though being more accurate is nice) but rather reproduction of trends. That 30% error is not large enough to say that the warming trend isn't happening nor is it large enough to invalidate the conclusion that humans are the cause.

"Prediction is very difficult, especially about the future" Nobody doubts Mr Berra's famous truism. Prediction about the past, however, is ridiculously easy. If I had enough data, I could tell you what you had for breakfast yesterday. But would that convince anyone that I had the authority to tell you what to eat tomorrow?

If you developed a reasonable physical model using the past data and validated it by making predictions about the future that are later validated (which climate scientists have done) then yes clearly you've got a model worth listening too. But actually what we're discussing now is not actually predictions about the future. Right now we're discussing the validity of physical models and the interpretation of the models. Specifically the climate models we are discussing are not evidence for human caused global warming because they predict the future. They are evidence for human caused global warming because they accurately model the historical recorded using the physical processes that clearly indicate humans have caused the change in climate.

Even if you do not believe the future predictions of the climate models and even if the future predictions are not 100% accurate that does not change the fact that the physical modeling of the past proves humans have caused the observed climate change. Given that we are currently changing the climate and that the changes have the potential to be very harmful (even if you think the chances are small) to most of the planet we have a duty to attempt to mitigate our impact on the climate despite our inability to make 100% accurate predictions about the future. The regulation of carcinogens is a prime example of this principle in action. Even given data on the exposure of a population to a carcinogen we cannot accurately predict which individuals will get cancer nor when. However, based on verified physical models and past data we know that the presence of that carcinogen has the potential to be harmful.

Also none of your points above address the very simple fact that we've directly measured an imbalance in infrared radiation entering and leaving the upper atmosphere that matches the energy needed to explain the observed temperature increases. The only possible reason for this imbalance is the greenhouse effect and the only significant source of new greenhouse gasses is human activity. Even if you disagree with the climate models we've now directly measured the greenhouse effect in action.

[Bored chemist]

To Bored Chemist,

It would be really nice to know what it would take in your case.

As I have said before, The first step would be to explain how adding CO2 didn't cause warming.
It's a greenhouse gas.
You would need to explain how it somehow didn't raise the temperature.

Nobody yet has got close to doing that.

BTW, Alan, Maggie destroyed the mining industry because the unions were a strong voice opposing hers. It had nothing to do with climate change.

Also, speaking out in favour of a century old technology that's 97% inefficient is "interesting".
If you find that fluorescent lights are toxic, I suggest that you stop eating them.

So data from the world showing that it was not warming would not do it.

If it got colder would that do it?

If the IPCC's predictions were narrowed down to the low end of the range at which there is almost no cause for concearn would you then think there was nothing to worry about?

You see I am not trying to disprove the science of IR absorption I just want to know what level of warming is OK and how you would get to that position.

Well, since the world is warming  that's an entirely irrelevant question
But, since I'm debating climate change with someone who doesn't want to believe in it, I guess I have to put things like that to one side.
After all, it's only a fact.

OK, so the answer to your question is simple.
Even f the world were getting colder the effect of CO2 would still be to raise the temperature and that's warming.
If some external effect- perhaps God built a really big deep freeze or something- overruled that effect it wouldn't mean the effect wasn't there.
So, mankind 's actions would still be warming.

[Bored chemist]

We know that, but the trick is to get the population to believe that what she did was a Good Thing. The UK now sits on about 200 years' supply of coal that cannot be mined safely or economically, ever. If were was no mitigating factor, the Conservative party would be unelectable, and we can't have that, can we? 

Also, speaking out in favour of a century old technology that's 97% inefficient is "interesting".

I used to heat my kitchen with 500W of tungsten lighting. When I replaced the bulbs with CFLs, I had to install bigger radiators to make up the deficit. Trouble is that the radiators heated the walls and windows, whereas the lamps used to heat the people, so the net efficiency decreased. I've no objection to CFL and LED lighting where heating is undesirable and long life is essential, but it would be nice to have an efficient ceiling-mounted radiant heater again!   

Apropos your main point, however, the earth's climate is such a complex system that, even though it is scientifically obvious that CO2 is not a significant driver, it would be very difficult to produce a realistic and predictive model based on water, the major greenhouse gas.  The only way to convince anyone who isn't impressed by simple physics (i.e. most people) is to wait until the temperature starts to decrease whilst CO2 remains constant or increases. By that time, however, I'm sure everyone will have lost interest and a bigger bogeyman will be foisted upon the taxpayer.. It's worth remembering that income tax, believed by most people to be as essential as DNA, was actually introduced as a temporary measure to pay for the Napoleonic Wars. How short the public memory....

"We know that, but the trick is to get the population to believe that what she did was a Good Thing. The UK now sits on about 200 years' supply of coal that cannot be mined safely or economically, ever. If were was no mitigating factor, the Conservative party would be unelectable, and we can't have that, can we? "
The lie told at the time was that UK coal was too expensive.
It wasn't true then; it isn't true now and it has nothing to do with climate change since it was done when people were not really looking at that.

Maggie did not say "we have to close the pits because of global warming".
So you are posting a red herring.
Please stop doing so.

"I used to heat my kitchen with 500W of tungsten lighting. When I replaced the bulbs with CFLs, I had to install bigger radiators to make up the deficit. Trouble is that the radiators heated the walls and windows, whereas the lamps used to heat the people,"
To exactly the extent that the light didn't shine on the walls- i.e. zero.
That claim just doesn't stack up with the laws of physics.
However, if you really want to "keep the faith" buy some halogen lamps and burn half a KW heating the room (it won't work unless the room is uncommonly well lagged- but why let reality get in the way) .

In the meantime, perhaps you could look at the cost of a KWHr of electricity, and the same energy from gas.
Feel free to use the energy that's more expensive- but don't blame the government for encouraging people not to join you in that folly.

"Apropos your main point, however, the earth's climate is such a complex system that, even though it is scientifically obvious that CO2 is not a significant driver"
It is neither obvious, nor scientific.
And for what it's worth, you have made no attempt to show that it's even true.

You seem to be as guilty of "slight of hand" as the governments you criticise.
Now I agree with you that they are playing silly buggers with just about everything, but occasionally they get irt right . AGW is one of those (though it took long enough)