What is the correct value of Climate Sensitivity?

[waldo]

Its OK Waldo. All we have to do is build some dams. I heard it right here.

what's worse is the "moderator" chose to delete my last post and tag me with a warning point... claiming it was "off topic/thread jacking"... that I was trolling! I'll try it again:

I agree with the IPCC's statement. But more than half != nearly all. The use of 'nearly all' in the article is spin.

no - the article is not spinning anything... and you continue to ignore the full attribution statement; in fact, the second time you purposely omit the pertinent bold-highlighted part of the the statement I quoted from that IPCC attribution statement. Again, that related statement from the IPCC:

are you having trouble with the full related IPCC attribution statement? (re: AR5 WG1 10.3)

It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.

for the "moderator's" particular notice: the last sentence of the above IPCC attribution statement is the reference that speaks to the extent of the anthropogenic basis for today's relatively recent warming; i.e., there is no presumed, as claimed "alarmist spin" in the earlier referenced article. In my earlier (now deleted) post I put forward the following 2 graphics which speak to a/the pertinent figure within the IPCC report that is (a part of) the basis for the attribution statement's last sentence... as well as an interpretation on that report graphic which particularly speaks to the last sentence of the above attribution sentence. Again... the last sentence that is being purposely ignored both in interpretation as well in the re-quoting of my post: Again, those 2 related graphics, as follows... graphics that are not, as stated by the "moderator", trolling... that are not, as stated by the "moderator", off-topic... that are not, as stated by the "moderator", thread-jacking!

an interpretation of the above IPCC Figure 10.5, per RealClimate/climate scientist Gavin Schmidt:

.

[waldo]

The actual science (meaning peer reviewed literature) says that there is no evidence that current weather patterns are different from historical norms. This includes droughts, rain events and storms. The only weather events which have increased are high temperature extremes but those extremes are matched by a corresponding decrease in cold weather extremes (which are much worse for humans which means warming is actually good for humans).

no - that is not correct. Certain differences, other than temperature extremes, have been shown to exist on regional levels... you know, those levels that actually mean something to directly affected people dealing with the impacts.

care to put up a cite to substantiate your claim of "matching/offsetting" cold versus hot/high temperature extremes?

[TimG]

http://www.nature.com/nature/journal/v491/n7424/abs/nature11575.html

More realistic calculations, based on the underlying physical principles8 that take into account changes in available energy, humidity and wind speed, suggest that there has been little change in drought over the past 60 years.

Kunkel et al. (2008) found that the United States has experienced a general decline in cold waves over the 20th century, with a spike of more cold waves in the 1980s.

http://diginole.lib.fsu.edu/cgi/viewcontent.cgi?article=1039&context=coaps_pubs

Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40‐years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low.

[-1=e^ipi]

You definitely know your material. So you believe humans are driving climate change, which is what I suspected. do you feel humans are causing all the strange weather the globe is experiencing?

That's a very difficult question to evaluate or answer because 'strange weather' is not very well defined, plus weather is chaotic.

I don't think it's possible to attribute a single strange weather event to human-caused climate change, regardless of how the media may portray a single hurricane or blizzard to global warming, because weather is chaotic. A better way to think about how climate change affects weather is to look at how it affects the probability distribution of weather. So if you observe a tornado in southern Ontario, you can't say 'this is clearly due to climate change' but you can say 'global warming is expected to increase the frequency of tornadoes in southern Ontario'.

The actual science (meaning peer reviewed literature) says that there is no evidence that current weather patterns are different from historical norms. The only weather events which have increased are high temperature extremes but those extremes are matched by a corresponding decrease in cold weather extremes (which are much worse for humans which means warming is actually good for humans).

Not sure I agree with this statement. I've seen some literature that suggests that rainfall patterns have changed slightly (even after taking into account natural climate variation) and should be expected to change based on paleodata, for example.

[-1=e^ipi]

The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.

This is a meaningless statement for a number of reasons.

For one, AR5 has no best estimate of climate sensitivity. In AR4 they had one (3.0 C for ECS), and claimed that climate models, radiative balance calculations using instrumental data, and paleodata were in agreement. Yet now that's not the case, why do you think that is?

Confirmation Bias. People start with a belief (CO2 is the main cause of observed warming) and then see if the belief is plausible based on the evidence, rather than try to obtain the best estimate of the magnitude of the effect of CO2 based upon the evidence (while including other factors that cause climate change). This has resulted in upward biases of the estimates of the magnitude of climate sensitivity, and now we are seeing the estimates being lowered.

For instrumental estimates, increases in GHG forcing is very strongly correlated with increases in negative aerosol forcing (due to coal) up until about the 1970s (when the clean air act was introduced). However, since the 1970s, the Atlantic Multidecadal Oscillation has been on a warming trend (arguably PDO and ENSO play a role here to). So one can make a plausible case for a high climate sensitivity which appears to fit the instrumental record if one simultaneously overestimates the effect of anthropogenic aerosols and underestimates the effect of the AMO; but while plausible, it would be a biased upward estimate because one is not looking at the best estimate based upon the data.

For paleo estimates, often they will conveniently ignore factors that have caused climate change in the past and falsely attribute this climate change to CO2 (since CO2 is a positive feedback, it is correlated with these other factors). In particular, paleoestimates that look at changes over the Pleistocene often completely ignore the effects of Milankovitch cycles (which are the ultimate cause of the ice ages) and don't take into account the non-uniform distribution of the effect of the ice-albedo effect (which is higher in polar regions, so not taking this into account will underestimate the relative strength of this effect to changes in GHG forcing due to the Stefan-Boltzman law). For estimates that use data before the Pleistocene, often they do not properly take into account the affects of the changes in the positions of the continents, and often they neglect the effects of N2O and CH4, which means that the estimates of climate sensitivity again have an upward bias.

For climate models, they all involve a number of parameters that need to be chosen using some a priori information, and it is difficult to evaluate whether the choice of these parameters biases the estimates and often it will cause climate models to be over-confident in their predictions. Furthermore, the construction of models and the choice of these parameters (and subsequent changing of the parameters when they don't meet expectations), means that they are very vulnerable to confirmation bias. In particular, if the climate models are generally overestimating the effect of greenhouse gases, overestimating the effect of aerosols and underestimate natural variability then they can appear to be reasonable based on instrumental data, but give very biased predictions (as we have seen in the fact that climate models over greatly overestimated the expected warming over the past decade). Two recent papers by Bjorn Stevens are relevant here: one that greatly reduced the upper bound on the effect of Aerosols (which when taken into account reduces estimates of climate sensitivity http://judithcurry.com/2015/03/19/implications-of-lower-aerosol-forcing-for-climate-sensitivity/),and one that showed evidence for an 'Iris effect', which basically all climate models are not taking into account.

A second reason why this statement is a bit meaningless is is that often estimates of climate sensitivity don't simultaneously determine the impulse response function, which means they can't properly evaluate the fraction of warming caused by greenhouse gases. So that leaves only climate models (although there are a few exceptions such as Van Hateren 2012) that are being used to evaluated the fraction of warming, and these models are again subject to their own biases and are generally giving estimates of climate sensitivity much higher than the instrumental data suggests (CIMP5 models have a median climate sensitivity of ~3.2 C).

there is no presumed, as claimed "alarmist spin" in the earlier referenced article.

They take a very specific claim about being more than 95% confident that more than 50% of observed warming since 1950 is due to greenhouse gases, and spin that to mean 'nearly all' recent warming is due to greenhouse gases. That's spin. What is 'nearly all'? More than 95%?

1. This is using biased estimates of the effects of greenhouse gases and Aerosols. One thing to look out for is that the IPCC uses subjective Bayesian priors in the determination of their pdfs, which means that many of their pdfs are biased (http://climateaudit.org/2015/04/13/pitfalls-in-climate-sensitivity-estimation-part-2/).

2. It appears to me that this is just looking at forcing changes over this period (correct me if I'm wrong), which won't properly take into account the fact that the temperature response is delayed. In particular, solar irradiance has has a relatively flat trend since 1950, but from 1700-1950, it was increasing by a fair amount. Since the temperature response is delayed, some of the warming since 1950 should be attributed to changes in solar irradiance, yet the median of the 'estimates' of NAT and internal variability are zero...

.

Even if I were to accept this figure, which I do not, the figure suggests that we are not 95% certain that at least 90% of warming since 1950 is due to human activity (I wonder if aerosols are being excluded from this definition of 'human activity'). So again, the claim that the IPCC is very certain that nearly all warming since 1950 is spin, and arguably scientifically inaccurate. Of course, I still don't have a precise definition of nearly all, so could you provide me with one? What percentage of warming since 1950 has to be anthropogenic in order for it to be considered nearly all?

[-1=e^ipi]

care to put up a cite to substantiate your claim of "matching/offsetting" cold versus hot/high temperature extremes?

TimG has already substantiated his claim, but thought I would provide this link as well to a recent study.

http://joannenova.com.au/2015/05/study-on-74-million-deaths-cold-weather-kills-20-times-more-than-heat-does/

Also in response to the claim provided by TimG:

Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40‐years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the global frequency of tropical cyclones has reached a historical low.

My understanding is that the frequency of tropical cyclones is expected to decrease due to increased greenhouse gases because these greenhouse gasses reduces the availability for tropical adiabatic instability, which allows tropical cyclones to exist.

[TimG]

Not sure I agree with this statement. I've seen some literature that suggests that rainfall patterns have changed slightly (even after taking into account natural climate variation) and should be expected to change based on paleodata, for example.

I guess there are some small increases in rain fall. My main point was to address the myth that droughts and hurricanes are increasing because of warming.

[socialist]

That's a very difficult question to evaluate or answer because 'strange weather' is not very well defined, plus weather is chaotic.

I don't think it's possible to attribute a single strange weather event to human-caused climate change, regardless of how the media may portray a single hurricane or blizzard to global warming, because weather is chaotic. A better way to think about how climate change affects weather is to look at how it affects the probability distribution of weather. So if you observe a tornado in southern Ontario, you can't say 'this is clearly due to climate change' but you can say 'global warming is expected to increase the frequency of tornadoes in southern Ontario'.

Not sure I agree with this statement. I've seen some literature that suggests that rainfall patterns have changed slightly (even after taking into account natural climate variation) and should be expected to change based on paleodata, for example.

I remember watching an Inconvenient Truth and becoming very frightened. When all the Arctic ice melts and a good chunk of Antarctic ice melts, then we are doomed. There is no debate around that. Rising sea levels will destroy Earth.

So basically you are saying that the Dust Bowl conditions of the 1930s were not caused by human actions? Then what caused that long drought? How much higher is the average temperature due to human habits?

[-1=e^ipi]

I remember watching an Inconvenient Truth and becoming very frightened. When all the Arctic ice melts and a good chunk of Antarctic ice melts, then we are doomed.

Ominous music while showing annual ice melt during the summer (which happens every summer) can be very misleading. I wouldn't consider Inconvenient Truth to be a scientifically accurate portrayal of climate science.

There is no debate around that. Rising sea levels will destroy Earth.

There is plenty to debate. For one, what is the scientific definition of 'doomed'? I'm also not sure I would consider the Earth to be destroyed due to sea level rise. The ice caps have melted before and the Earth wasn't destroyed (actually for most of the past 500 years the earth has had no glaciated polar ice caps).

So basically you are saying that the Dust Bowl conditions of the 1930s were not caused by human actions?

With respect to the Dust Bowl in particular, a lot of it had to do with human agricultural practices in North America, but that is not the same thing as human greenhouse gas emissions. With respect to the unusually warm temperatures during that period & drought, that was primarily natural.

How much higher is the average temperature due to human habits?

Off the top of my head, current global temperature are about 0.5-0.6 C warmer today due to human emissions.

[socialist]

Ominous music while showing annual ice melt during the summer (which happens every summer) can be very misleading. I wouldn't consider Inconvenient Truth to be a scientifically accurate portrayal of climate science.

There is plenty to debate. For one, what is the scientific definition of 'doomed'? I'm also not sure I would consider the Earth to be destroyed due to sea level rise. The ice caps have melted before and the Earth wasn't destroyed (actually for most of the past 500 years the earth has had no glaciated polar ice caps).

With respect to the Dust Bowl in particular, a lot of it had to do with human agricultural practices in North America, but that is not the same thing as human greenhouse gas emissions. With respect to the unusually warm temperatures during that period & drought, that was primarily natural.

Off the top of my head, current global temperature are about 0.5-0.6 C warmer today due to human emissions.

0.5 is too much. That is a dangerous increase as I'm sure you agree. y doomed I mean coastal cities being flooded and destroyed. It seems to me that humans are driving global warming and it may be too late to change things. We need to eliminate ALL use of fossil fuels. I think you understand the dire situation the globe is in. What do we need to do? We need to get back to walking more and riding bikes and planting more trees. But corporate greed is destroying green spaces which is also causing global warming. Things will be very scary by 2020.

[waldo]

are you having trouble with the full related IPCC attribution statement? (re: AR5 WG1 10.3)

It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.

This is a meaningless statement for a number of reasons.

For one, AR5 has no best estimate of climate sensitivity. In AR4 they had one (3.0 C for ECS), and claimed that climate models, radiative balance calculations using instrumental data, and paleodata were in agreement. Yet now that's not the case, why do you think that is?

you appear to improperly equate climate sensitivity to total warming - yes?. As for why the IPCC didn't include a best estimate for ECS within AR5, I interpret that, for studies that fit within the AR5 publishing window, to relate to discrepancies between observation based estimates versus climate model estimates... in a most active area of continuing research. I suggest if you, as you did, want to speak to "Confirmation Bias", you personally may want to consider your own apparent leaning that clearly presumes uncertainty only applies to high(er) end estimates... it should be obvious to even you that uncertainty doesn't just cut one way! In any case, post AR5, published studies continue to come forward with results that support ECS values similar to the ~3ºC CMIP5 model mid-range... along with papers that take a critical review of the temperature/forcings 'energy budget' approach taken by recent profiled lower sensitivity estimate papers in properly accounting for the role of the oceans in taking up excess heat. Again, a most active area of ongoing research...

but really, why are you choosing to singularly emphasize and speak to sensitivity... with its projection emphasis and short/long-term feedback attachments, as a reflection on the attribution of the relatively recent past (6 decades of) warming? In line with your comparative AR4-to-AR5 reference, in terms of an attribution statement on the most likely amount of anthropogenic warming, it was the AR4 statement that didn't include a "best estimate" value for the anthropogenic contribution to past warming. However, it is the AR5 statement that does include a best estimate; one where the anthropogenic contribution is close to the observed estimate... where, again as stated in my earlier post; "The best estimate of the human-induced contribution to warming is similar to the observed warming over this period"... implying that the best estimates of net natural forcings and internal variability are close to zero as summarily represented/supported by the graphic I provided per Figure 10.5 of IPCC AR5 WG1 10.3. Again:

the pdf I referenced, based upon that IPCC Figure 10.5, extends on that ~100% anthropogenic contribution to warming to present a mean of 110%... effectively accounting for the slight cooling effect of natural factors... again, that pdf based upon the same IPCC AR5 WG1 Figure 10.5 (where combined anthropogenic forcings (ANT) is around 0.7 ± 0.1ºC, and the observed temperature (Observed) is about 0.65 ± 0.06ºC). Whether you personally choose to accept that pdf (again, as below) is irrelevant... the basis for the IPCC attribution statement and that summary Figure is substantiated within Chapter 10 of that IPCC AR5 WG1 report. Again:

you can stifle your expressed wonder as, no... the cooling effect of aerosols is not excluded from the grouping "other anthropogenic forcings (OA within Figure 10.5)"; most pointedly, per the same IPCC WG1 10.3 report:

"Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3°C over the period 1951 to 2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C. The contribution from natural forcings (solar irradiance and volcanic aerosols) is likely to be in the range of −0.1°C to 0.1°C, and from natural internal variability is likely to be in the range of −0.1°C to 0.1°C. Together these assessed contributions are consistent with the observed warming of approximately 0.6°C to 0.7°C over this period."

through all your meandering scattered writing, you presume to attach "some degree" of warming influence to natural forcing and internal variability... yet somehow you never manage to actually qualify/quantify anything. Your unsubstantiated suggestion to the influence of a "delayed response to solar irradiance"... is meaningless..

[-1=e^ipi]

0.5 is too much. That is a dangerous increase as I'm sure you agree.

I'm not sure I agree.

y doomed I mean coastal cities being flooded and destroyed. It seems to me that humans are driving global warming and it may be too late to change things.

Sea level rise reaches equilibrium over a very long time scale (decay rate to equilibrium is like 400-500 years so it takes ~2000 years to reach equilibrium. As a result, there is more certainty over expected sea level rise then expected change in temperature over the next century. It is expected that we will see ~0.5 m of sea level rise by the end of the century (with the 95% confidence interval under a large variety of emission scenarios being from about 0.3 m - 0.8 m according to IPCC AR5). We also have a Paleoclimate estimate of the change in sea levels due to a change in global temperature thanks to the Eeemian (last interglacial, which was warmer than today). The equilibrium change in sea level due to an increase in global temperatures by 1 C is about 3 m.

We need to eliminate ALL use of fossil fuels..

Why?

What do we need to do?

More paleoclimate data on climate change over the Holocene and better instrumental coverage of places like Africa, the Arctic Ocean, Antarctica, Northern Australia and other locations on Earth where data is sparse would be nice.

We need to get back to walking more and riding bikes and planting more trees. But corporate greed is destroying green spaces which is also causing global warming.

I think you are mixing up deforestation with CO2 emissions.

[waldo]

Further to that the continuing melting of parts of Greenland, Antarctica and the Arctic Ice pack may be from the ending of the Ice Age. It takes a while for accumulated ice to melt under temperatures that warmed after the last Ice Age.

your consistent 'hobby-horse' claims that today's relatively recent warming is due to the earth "coming out of the LIA" have been dispensed with many times over in past posts... yet you continue with your same, always UNSUBSTANTIATED, statement/claim in that regard - go figure!

[waldo]

The only weather events which have increased are high temperature extremes but those extremes are matched by a corresponding decrease in cold weather extremes

no - that is not correct. Certain differences, other than temperature extremes, have been shown to exist on regional levels... you know, those levels that actually mean something to directly affected people dealing with the impacts.

care to put up a cite to substantiate your claim of "matching/offsetting" cold versus hot/high temperature extremes?

TimG has already substantiated his claim, but thought I would provide this link as well to a recent study.

http://joannenova.com.au/2015/05/study-on-74-million-deaths-cold-weather-kills-20-times-more-than-heat-does/

say what! There's nothing in what member 'TimG' presented (as presumed citation)... and there's nothing in your link reference that speaks to anything along the lines of the claim that, "high temperature extremes are matched by a corresponding decrease in cold weather extremes"

care to try again?

[waldo]

I guess there are some small increases in rain fall. My main point was to address the myth that droughts and hurricanes are increasing because of warming.

My understanding is that the frequency of tropical cyclones is expected to decrease due to increased greenhouse gases because these greenhouse gasses reduces the availability for tropical adiabatic instability, which allows tropical cyclones to exist.

formal/recognized claims on extremes have not included reference to an increase in the activity (frequency of) tropical cyclones... but yes, only on a regional level, have statements qualified an increase in their intensity. Equally, member TimG doesn't delineate his statements in terms of regional versus global.

[-1=e^ipi]

you appear to improperly equate climate sensitivity to total warming - yes?.

No.

As for why the IPCC didn't include a best estimate for ECS within AR5

So you admit that an IPCC best estimate no longer exists. Good.

I suggest if you, as you did, want to speak to "Confirmation Bias", you personally may want to consider your own apparent leaning that clearly presumes uncertainty only applies to high(er) end estimates... it should be obvious to even you that uncertainty doesn't just cut one way!

You are mixing up bias of an estimate with uncertainty of an estimate.

In any case, post AR5, published studies continue to come forward with results that support ECS values similar to the ~3ºC CMIP5 model mid-range...

Yes because some people are continuing with their confirmation bias to get biased results. The instrumental data and Pleistocene ice-core data both exclude an ECS greater than 3 C at the 95% confidence level if you properly take into account all the main factors that cause changes in global temperature. Some climate scientists are using new evidence (such as the two papers by Bjorn Stevens) to get more reasonable estimates of climate sensitivity (ECAM6 gets an ECS of ~2.2C, down from 2.8C after taking into account the Lindzen Iris effect for example).

along with papers that take a critical review of the temperature/forcings 'energy budget' approach taken by recent profiled lower sensitivity estimate papers in properly accounting for the role of the oceans in taking up excess heat. Again, a most active area of ongoing research...

Interestingly, everyone was all fine with energy budget calculations when they were getting median sensitivity estimates of 3.0 C, but now that they are getting estimates about half that with updated aerosol data, suddenly energy budget calculations are no longer good.

Anyway, Nic Lewis has recently come out with a new paper (http://climateaudit.org/2015/06/02/implications-of-recent-multimodel-attribution-studies-for-climate-sensitivity/) that shows that some of the papers used in AR5 (Gillette et al. 2013, Jones et al. 2013) give overestimates of climate sensitivity due to their usage of subjective Bayesian priors.

but really, why are you choosing to singularly emphasize and speak to sensitivity...

Because understanding the magnitude of warming is relevant to trying to understand what is the best policy response to the issue of climate change.

with its projection emphasis and short/long-term feedback attachments, as a reflection on the attribution of the relatively recent past (6 decades of) warming?

Wow, no. ECS is the equilibrium temperature response expected due to a doubling of atmospheric CO2 when only taking into account 'fast' feedbacks (i.e. excluding ice-albedo, ocean-albedo and vegetation-albedo feedbacks; so only including feedbacks with decay times of about 100 years or less). For one, we haven't doubled atmospheric CO2 yet, and secondly 6 decades is no where near enough time to reach the ECS even if we did. That is even a lower timescale than what is used to calculate the transient climate response (TCR), and again we haven't doubled CO2 (we've done about half a doubling), so recent warming due to CO2 is going to be less than half the TCR, which is what is observed.

implying that the best estimates of net natural forcings and internal variability are close to zero

No that doesn't imply that. Read my comments about simultaneously overestimating climate sensitivity, the effect of aerosols and underestimating the AMO to get a set of claims that appears to explain the instrumental data.

the pdf I referenced, based upon that IPCC Figure 10.5, extends on that ~100% anthropogenic contribution to warming to present a mean of 110%... effectively accounting for the slight cooling effect of natural factors... again, that pdf based upon the same IPCC AR5 WG1 Figure 10.5 (where combined anthropogenic forcings (ANT) is around 0.7 ± 0.1ºC, and the observed temperature (Observed) is about 0.65 ± 0.06ºC). Whether you personally choose to accept that pdf (again, as below) is irrelevant... the basis for the IPCC attribution statement and that summary Figure is substantiated within Chapter 10 of that IPCC AR5 WG1 report. Again:

I've already expressed my reasons for doubting how Gavin Schmidt interprets Figure 10.5. It only looks at changes in forcings, so doesn't take into account the fact that warming is delayed; it is misleading to just look at forcing changes over a period and expect that the proportion of forcing changes over that period is identical to the proportion of temperature changes caused by the different factors; in particular it would ignore the fact that increase in solar irradiance from 1700-1950 would cause some of the observed warming from 1950 to present. And again, there is the issue over overestimating the effect of aerosols to simultaneously overestimate the effect of greenhouse gases.

where combined anthropogenic forcings (ANT) is around 0.7 ± 0.1ºC

Radiative forcing is power per unit area (example: W/m^2), not temperature (such as Celcius).

including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C.

Again, the recent paper by Bjorn Stevens shows that the lower bound on this estimate of aerosols is too low.

The contribution from natural forcings (solar irradiance and volcanic aerosols) is likely to be in the range of −0.1°C to 0.1°C

What's their methodology for determining this? Because it needs to adequately take into account the delay in warming, not just look at changes in forcing.

you presume to attach "some degree" of warming influence to natural forcing and internal variability... yet somehow you never manage to actually qualify/quantify anything.

Would you like me to use my results that I got when I tried to estimate a Van Hateren impulse response function from the Instrumental and Holocene Paleoclimate data to try to quantify this for you?

Your unsubstantiated suggestion to the influence of a "delayed response to solar irradiance"... is meaningless..

Again, I'm waiting for you to define 'nearly all'. More than 95%? More than 90%? Because if you accept that figure by Gavin Schmidt, then you should accept that we are not 95% certainty that 'nearly all' recent warming is due to greenhouse gasses (unless your definition of nearly all is greatly divergent from mine).

Edited June 5, 2015 by -1=e^ipi

[socialist]

I'm not sure I agree.

Sea level rise reaches equilibrium over a very long time scale (decay rate to equilibrium is like 400-500 years so it takes ~2000 years to reach equilibrium. As a result, there is more certainty over expected sea level rise then expected change in temperature over the next century. It is expected that we will see ~0.5 m of sea level rise by the end of the century (with the 95% confidence interval under a large variety of emission scenarios being from about 0.3 m - 0.8 m according to IPCC AR5). We also have a Paleoclimate estimate of the change in sea levels due to a change in global temperature thanks to the Eeemian (last interglacial, which was warmer than today). The equilibrium change in sea level due to an increase in global temperatures by 1 C is about 3 m.

Why?

More paleoclimate data on climate change over the Holocene and better instrumental coverage of places like Africa, the Arctic Ocean, Antarctica, Northern Australia and other locations on Earth where data is sparse would be nice.

I think you are mixing up deforestation with CO2 emissions.

So on a scale of 1-10, what impact do you feel humans are having on global warming? 10 being high.

Why are a majority of scientists and experts like waldo so concerned then? They can't all be wrong. Deniers are ridiculed for good reason.

If human habits don't change, what do you fell the earth will be like by 2030?

[TimG]

Why are a majority of scientists so concerned then? They can't all be wrong. Deniers are ridiculed for good reason.

First, climate scientists may have a reason to be concerned because there is a hypothetical problem. The issue is climate scientists have no business lecturing society on how to respond to the hypothetical risk because they have no special qualifications that allow them to understand the economic and social costs associated with reducing CO2 emissions. In many cases, dealing with these competing requirements needs a value based decision which everyone is qualified to have an opinion on.

Second, the "consensus" is exaggerated by various activists like waldo who want to push what is basically a left wing political agenda under the guise of "saving the planet". This leads them to unreasonably reject options like adaption or nuclear. They claim to care about the science but that is a sham that becomes obvious whenever a solution that is supported by the science (i.e. nuclear or fracking) presents itself but goes against their political prejudices.

Third, the use of the word "denier" is an example of the political nature of climate change activists because they apply to everyone who disagrees with their policy choices no matter what they may think about the science. It is an attempt to de-legitimize opposition and prevent a meaningful debate on the options. Anyone who uses the word "denier" is looking for an excuse to avoid having a political discussion.

Edited June 5, 2015 by TimG

[eyeball]

The issue is climate scientists have no business lecturing society on how to respond to the hypothetical risk because they have no special qualifications that allow them to understand the economic and social costs associated with reducing CO2 emissions.

There is no issue. The developed world's national scientific academies representing the vast VAST majority of all the sciences including economic, social and political are who's qualified. These are who should be lecturing society and policy makers on the facts and the implications of the facts the climate scientists have presented to them.

It is well past the time that politicians start regarding deniers as being on par with 9/11 truthers and it is also past the time that voters hold politicians who refuse to realize this in the same contempt the vast VAST majority scientists do.

Edited June 5, 2015 by eyeball

[-1=e^ipi]

So on a scale of 1-10, what impact do you feel humans are having on global warming? 10 being high.

I am not sure I understand your question. Are you asking about the magnitude of human greenhouse gas emissions on global temperatures, or are you asking what proportion of recent warming has been due to humans?

They can't all be wrong.

Wrong about what exactly? You haven't defined for me exactly what they may or may not be wrong about.

If human habits don't change, what do you fell the earth will be like by 2030?

Using a very rough calculation (assuming average annual increase in CO2 of 2.11 ppm per year, using a TCR of 1.5, and assuming that warming over this period will be roughly proportional to the TCR times the fraction of doubling of CO2 over this period), I get ~0.2 degrees warmer than today by 2030. Of course, lower aerosol emissions, increased CH4 emissions and increased N2O emissions would increase this slightly, but that will likely be offset by the Atlantic Multidecadal Oscillation.

[TimG]

There is no issue. The developed world's national scientific academies representing the vast VAST majority of all the sciences including economic, social and political are who's qualified.

What unmitigated BS. Statements made by science academies do NOT represent the opinions of the scientists that belong to them. The statements made only represent the opinion of the tiny minority on the committee that drafted the statement. The APS recently responded to complaints about its 2007 statement by having a process to actually get input from members. The trouble is this process did not give the answer the leadership wanted so they ignored the input and just re-iterated the BS from 2007.

These are who should be lecturing society and policy makers on the facts and the implications of the facts the climate scientists have presented to them.

Again BS. The people that matter when it comes to questions of what to do about climate change are the engineers and managers involved in actually keeping the power on today. These are the only people with the expertise to know the true cost of changing to alternate power sources (or if it is even technically feasible). Once you know the costs the everyone is entitled to an opinion on what technically feasible options are worth paying for. People who claim that we should pass a law requiring unicorns because some activists claim we have to have unicorns are deluding themselves. Edited June 5, 2015 by TimG

[-1=e^ipi]

Now that I've read more into it, I don't think I should have used HadCRUT4 temperature data because as far as I can tell it doesn't properly deal with the coverage bias, particularly in polar regions. GISS and NOAA data sets also have this issue. So using one of these data sets probably results in an underestimate of climate sensitivity due to polar amplification. The Cowtan & Way (http://www-users.york.ac.uk/~kdc3/papers/coverage2013/series.html) as well as the Berkeley Earth (http://berkeleyearth.org/land-and-ocean-data/) data sets seem to address this issue adequately by using kriging (http://en.wikipedia.org/wiki/Kriging).

[socialist]

I am not sure I understand your question. Are you asking about the magnitude of human greenhouse gas emissions on global temperatures, or are you asking what proportion of recent warming has been due to humans?

Wrong about what exactly? You haven't defined for me exactly what they may or may not be wrong about.

Using a very rough calculation (assuming average annual increase in CO2 of 2.11 ppm per year, using a TCR of 1.5, and assuming that warming over this period will be roughly proportional to the TCR times the fraction of doubling of CO2 over this period), I get ~0.2 degrees warmer than today by 2030. Of course, lower aerosol emissions, increased CH4 emissions and increased N2O emissions would increase this slightly, but that will likely be offset by the Atlantic Multidecadal Oscillation.

You sure know your stuff. I'm learning a lot reading your posts. I used to think waldo was the expert on this topic, but you are making waldo seem like an ideologue.

I guess my new question is why has climate change been so mainstream and treated as a fact if in fact, as you say, it is not? Tim alluded to a possibility that this is a left wing political agenda, pushed by non-scientists like waldo, but I don't understand that. Is this more about politics than about science? What is the end game?

[TimG]

Is this more about politics than about science? What is the end game?

It has to do with the "solutions". The left sees corporations as the enemy and the government as good. CO2 regulation is a means to control corporations and direct more resources to the government. i.e. instead of the market deciding which companiees succeed or fail in a world governed by CO2 regulations would see that only government approved corporations have a chance of succeeding. On top of that the left sees CO2 regulation as a excuse to transfer money from the rich to the poor.

To be fair, the first instinct of people on the right is to oppose CO2 regulations for the exact same reason and that leads some of them to make rediculous statements about the state of the science. Conversely, you have many left wing activists who make claims that have no connection with what the science says and try to usurp the authority of science to discourage people from questioning their pet policy choices.

Edited June 6, 2015 by TimG

[-1=e^ipi]

I guess my new question is why has climate change been so mainstream and treated as a fact if in fact, as you say, it is not? Tim alluded to a possibility that this is a left wing political agenda, pushed by non-scientists like waldo, but I don't understand that. Is this more about politics than about science? What is the end game?

'Climate change' in the context of your sentence is really vague. The climate has always changed, although recent warming has been caused by increased levels of greenhouse gasses. But the fact that there is climate change and humans are causing some of it doesn't tell us what the optimal policy response to the issue is. In fact, the scientific method can't tell us what the optimal policy response is because the scientific method is not capable of telling people what to do. To figure out what is the best policy response requires a set of value judgements (the pareto principle is a good place to start).