In a report released just before Christmas, the UK Met Office lowered its decadal forecast for the expected average global temperature. The press release noted that:
Global average temperature is expected to remain between 0.28 °C and 0.59 °C (90% confidence range) above the long-term (1971-2000) average during the period 2013-2017, with values most likely to be about 0.43 °C higher than average. The warmest year in the 160-year Met Office Hadley Centre global temperature record in 1998, with a temperature of 0.40°C above long-term average. The forecast of continued global warming is largely driven by increasing levels of greenhouse gases.
This was a noticeable change from previous forecasts and was the result of a new climate model being put into use. The upper chart shown below portrays the earlier estimate of temperature rise while the lower chart shows the new estimate. The dark blue lines show the mean, with the light blue lines indicating an upper and lower bound.
The revision was initially ignored in the Christmas rush, but with the festive season now over, the story has reappeared. Some media outlets interpreted this as evidence that “global warming had stopped”, given that the medium term forecast was no different to the temperature peak seen in the late 1990s. One particular columnist caused the Met Office to release a point-by-point rebuttal of his claim that the Office was “useless”.
Despite the acrimony, the revision does raise the question as to what is happening. On the one hand we are seeing an increase in the number of severe heat events globally, yet on the other there has been seemingly little change in global average temperature for much of the last decade.
The starting point must always be the fact that the increase in CO2 in the atmosphere will create a global heat imbalance, at least until a new steady state is reached (e.g. through changes in cloud cover, surface albedo etc. ). That steady state will also take many centuries to reach, given the huge inertia in the climate system. Current estimates put the size of the imbalance at about 3 W/m2 (Hansen et. al., 2009), which although small compared to the total heat arriving from the sun is significant compared to swings over the past million years that have resulted in large shifts in planetary ice cover.
The imbalance is offset to a degree by the effect of aerosols, which scatter incoming solar radiation and therefore act as coolants. There remains considerable uncertainty in the science community regarding the extent of the aerosol impact and how it might be changing over time. For example, the recent (10 years) sharp increase in coal use in China, much of which does not have sulphur emission handling, may well be adding enough sulphur (an efficient coolant) in the atmosphere to dampen the warming trend that would otherwise be seen. The charts below show the various forcings and the net effect. The large error bar illustrates the uncertainty linked with aerosols, to the extent that the red line (GHGs) and blue line (Aerosols) could cancel if at the extremes of their respective ranges.
The proxy we use to “measure global warming” is the surface temperature record, because both a recorded history and derived history of this measurement exists and because it’s relatively easy to take the necessary measurements. In the case of the recorded history, it is typically 100-150 years, but in the UK it starts in 1659 (1772 for the daily series). But real “global warming” is far broader than this and includes ocean heating (surface and deep ocean) and land ice melting.
Take as an example land ice melting. There is good evidence that this has risen considerably in recent years, with both Greenland and Antarctica showing a combined reduction in ice mass of some 400 billion tonnes per annum. The amount of energy required to melt this much ice (to overcome the latent heat of fusion) is in the same ballpark as the energy required to raise the temperature of the atmosphere by 0.02 deg.C in a single year (a tenth of the expected decadal increase of 0.2 deg.C). A very simple (probably too simple as someone is bound to comment) analogy is a glass of iced water, which on a hot day will remain cold until the ice melts. Then the temperature starts rising rapidly – but this is not to argue that the climate system will do the same.
As the additional heat building up in the atmosphere distributes through the ocean/ice/atmosphere system it is unlikely that a uniform and unchanging temperature rise in one particular part of this system would be the result. The interaction between them and the impact of short term aerosols will likely result in volatility in the surface temperature record. This has been seen before, most recently in the post war period when temperature remained flat for about 20 years. Some have attributed this to the aerosol loading from the rapid increase in coal burning in the USA and Europe over that period, none of which had sulphur scrubbing. As sulphur emissions fell sharply with the arrival of scrubbers, so the masking effect was removed and temperatures began rising.
To simply argue that “global warming has stopped” is short sighted. The evidence to support such a claim is not there.
I would class this explanation as very poor. Global warming as measured by surface temperatures clearly slowed down. No doubt about that. Sure, the forcing from CO2 is increasing so computer gamers have no other option than to put some counter forcing in place to keep CO2 as a dominant player. Therefore, the chart of forcings is largely hypothetical. It is even missing solar forcing. The only solar signal it is using is a solar constant (called solar irradiance). It is simply ignoring last 50 years when the sun was at the grand solar maximum. What is the point of using solar constant for a model while ignoring solar activity (like solar wind and cosmic radiation) which has a strong signal?
Referring to alleged loss of ice in Greenland and Antarctica is dodgy at the best. First, Greenland is losing ice ever since the last ice age and will continue doing so until the next ice age. The monitoring of ice loss (through gravity anomaly measurement) is so inaccurate and short that there is no way to make any conclusions. The best way how to monitor ice loss is sea level. Unfortunately, this is again plagued with uncertainty. What I think we can say that the sea level is rising very slowly at the rate of few millimetres a year with no sign of acceleration.
So has the global warming stopped or not? I’m really not sure as there is insufficient monitoring to say conclusively. But, one thing is for sure. There is no acceleration in climate trends at all and if the current trends continue in the same way as they were over the last 150 years there is no cause for alarm at all. IPCC needs significant acceleration in warming to see their computer games being true.
I suspect that if I said the sky was blue you would doubtless post a comment saying that I was colour blind.
David, apologies for a perhaps naive question, but am I to understand Mt. Pinatubo is used as the source for claims as to “global” temps?
Re Mt Pinatubo, this is only in the diagram as a marker for when it happened, given it put a very significant volume of aerosol into the atmosphere which provided a temporary cooling.
Unfortunately, your ardent support for the IPCC’s status quo is being sorely tested. The Met. Office is in full scale dame limitation mode, as is the BBC. Both organisations have hitched their skirts to CO2-AGW and both now realise the World is undergoing rapid cooling as the Sun heads to its 1 in 179 year magnetic slumber. The threat is that they will be broken up into professional and propagandist sections with the latter thrown to the Wolves of private support.
The problem is that the IPCC science has been expertly faked and this has been revealed by real scientists collaborating World-wide via the internet. When I say faked, I really mean since 1997 when the bedrock of the CO2-religion, that CO2 caused the end of ice ages was disproved.
The bottom line is that this fake science is based on a 50 year old experimental mistake, to believe that pyrometers measure a real energy flux instead of temperature. Correct the ‘Energy Budget’ to account for this mistake and there is no CO2-AGW, nor can their ever be any – they have got it completely wrong!
According to the Met Office, there has been no statistically significant warming in ~16 years. According to the IPCC AR5 second draft, the adjusted temperature anomaly is below the lowest of the model projections.
Based on these two FACTS, I believe it is safe to conclude that the current climate models are flawed, though perhaps not as seriously as the model used to prepare his infamous presentation to the US Congress in 1988.
It should also be noted that the DATA from which the adjusted temperature anomaly is constructed are also flawed, in that they require “adjustment”. Recent studies suggest that up to half of the reported adjusted temperature anomaly is the result of the adjustments, rather than the underlying DATA.
You state that it is relatively easy to take the surface temperature measurements, yet I am sure you are aware that, on average, it is done exceptionally poorly, thus requiring “adjustment”.
May I point Jiri, Alec and Ed to this explanation of why AGW has not stopped in the last 16 years ? http://www.skepticalscience.com/16_more_years_of_global_warming.html
No, I would just point out that the sky is not always blue. Sometimes is black, sometimes is red, white or at some bad places it can be even yellow 🙂
Do you expect that everything in climate science is nice and clear? Maybe in the summary for policymakers.
Regarding Mt Pinatubo it was a major eruption placing a lot of aerosols and SO2 into the stratosphere were it can’t be washed out by rain. This causes warming of stratosphere but cooling of troposphere. Hansen and IPCC seem to be obsessed with human produced aerosols and SO2 which is released into the lower atmosphere causing acid rain and warming of troposphere. Surprisingly enough Hansen’s computer games claim that these anthropogenic aerosols are causing nearly as much cooling as major volcanoes. That is quite controversial but it is still IPCCs base case and it is used by some to justify a lack of global warming.
Sander, alarmist site named “skeptical science” (what a strange name for alarmist site isn’t it?) might be good for first introduction to the problem; however we need to dig deeper and look beyond the smoke screen. Let’s do that. Let’s do critical reading of:
First, when we talk about GISTEMP temperature series we should keep in mind that this series has incorrect interpretation of urban heat effect and uses extrapolation over wide territories. This is documented in scientific papers but will never be mentioned by IPCC. So the temperatures from cities and airports can be extrapolated over area several thousand kilometres wide.
Therefore, it is correct to use ocean heat content as a metric to measure global warming. However, Nuccitelli reconstruction is not something written in stone. The reliable OHC monitoring is possible only from 2005 when the ARGO system of buoys was in place. This system measures OHC down to 1000m depth making occasional measurements to 2000m depth. Based on this system we know that the oceans are absorbing less heat recently.
This is being picked up by many scientists. For example D.H. Douglass & R.S. Knox in their paper: http://www.pas.rochester.edu/~douglass/papers/PLA_21192_proofs_plusFigs1_2.pdf
This was obviously unacceptable to the climate alarmists who wrote their Nuccitelli counter paper cited by alarmist site “skeptical science”. Obviously, Douglass tried to correct this misinterpretation here:
Needless to say that “skeptical science” and IPCC will ignore this. This is how the climate wars are fought. “The team” of alarmist scientists are focusing to publish rebuttal to all inconvenient science. There have been cases when they tried to prevent publication of such papers by methods which I’m not ready to name here. This gives IPCC a cannonen fodder to cite papers they choose. Ignore inconvenient papers or just mention them briefly and put focus on convenient papers. This way we got hockey stick and many climate gate scandals when sloppy science was used in IPCC.
Finally, lobbyists like David who know nothing about the schism in the climate science (and very little about the science itself) come, take flawed IPCC report, cherry-pick the worst case warming, exaggerate it and use it to promote their agenda. They even go as far as citing Einstein who would be no doubt climate alarmist
The memo is that next time when you read “skeptical science” be sure that 100% of what they write is just a smoke screen to prevent you to see what’s happening beyond.
David refers to Hansen’s article (it’s not scientific paper).
He does that at climate legislation thread but the theme really belongs in here. I think that we need to do a critical reading to help David to understand significance (and mistakes) of this article.
First, 2012 was affected not only by relatively weak La Nina in the first half but by relatively weak El Nino in the second half as well. Hansen correctly assigns fluctuations on the annual scale to the ENSO cycle. However, he explains colder period of 1940-1975 on the basis of anthropogenic aerosol cooling. He fails to explain apparent colder period around 1910, he fails to explain little ice age, medieval climate optimum and all Holocene fluctuations. He has no forcings to explain these. However, there is a simple competitive observation based hypothesis. It is based on existence on several decadal oceanic cycles. For example pacific decadal oscillation with period of 60years ties perfectly to the warming and cooling cycles observed in the global temperature. Also it is known to cause unbalance in ENSO cycle. All good weathermen know that La Ninos were more likely in previous three decades. Hansen doesn’t know or ignores this. Instead he’s touting anthropogenic aerosols which allegedly rival effect of major volcanoes. This is purely hypothetical and not observation based.
This doesn’t prevent him to ignore various solar indices which are measured for decades and which reached unprecedented levels at the end of 20th century. E.g solar wind and cosmic ray activity proxies allow to estimate sun activity for hundreds if not thousands years back. Hansen ignores this. He finds this not convincing.
However, he acknowledges that in his models aerosols are just a fudge factor to tune greenhouse gas forcings to the observations and that GHG forcing is actually easing down despite increased emissions (due to the saturation of absorption bands).
He says that the planet is still in imbalance but he offers no proof for this claim. The satellite observations of radiative budget are not accurate enough and ocean heat content measurement is sort of reliable from 2005 and it is flat recently. This would suggest that the planet is at (or very close) to the energy balance at the moment.
Finally, he blames unforced climate variability for temporary halt in global warming – is he in odds with other alarmists denying the slowdown at all? He observed that in the last decade the first half was predominantly El Nino phase of ENSO while La Nina is dominating second half. This is only partially true. EL Nino was dominating last 30 years. Following 30 years La Nina is expected to dominate. This is based on reconstructions of PDO 60 years long cycle. Obviously, in Hansen’s models there is no allowance made for PDO or other multidecadal or longer climate cycles. Also he makes no allowance for solar cycles beyond negligible variability of solar (irradiance) constant.
Hansen’s hope for El Nino coming back strongly in next few years might be in vain. We can’t really expect very strong El Nino in 2013 due to the absence of warm water in pacific. Moreover he apparently doesn’t understand mechanism beyond ENSO. I’m not claiming that anybody understands completely, but it is clear that ENSO is coupled phenomenon of ocean cycle, solar forcing and atmosphere conditions (mostly clouds). Scientists say that we are in different climate mode in the last decade. The mode will have to switch again to return to warming. We saw this modes to switch approximately every 30 years so it would be rather unexpected if the mode switches again only after few years.
It looks like Hansen partly acknowledges failure of his model. If warming doesn’t return soon his model of solar insignificance is dead. I think that chances are very good that we will see very slow warming or even cooling over the next decade or two.
What does it mean for carbon trade lobbyists? Not too good. How can you incorporate carbon tax (or trade) when global warming is not happening? Extreme weather is just chasing a dead horse.