Are step changes in global temperatures ruled by ENSO and natural variability

[Sunny and Warm]

http://wattsupwithth...nso/#more-44897

Implications

It is demonstrated above that the temperature increase in the second half of the 20th century could have taken place in steps driven by major ENSO events. The significance of the finding does not mainly rest on the statistical significance of the model fit, but on the physical support of the ENSO observations for the step changes, identified without making a priori assumptions on the timing or number of steps.

If this was indeed the case – and it could be, unless proven otherwise – then the following implications arise:

1. Natural processes in the ocean-atmosphere system may have had a major influence on the global temperature change in the second half of the 20th century. If so, then something must be wrong with IPCC’s climate models, as the models according to the AR4 can not at all reproduce the observed temperature curve by considering natural causes only. This could question the climate sensitivity of the models and the models ability to adequately describe the natural processes in oceans and atmosphere (eg. ENSO phenomena). While it is generally accepted, that ENSO events can produce abrupt changes in global temperatures, the IPCC considers such effects to be short lived (albeit based on a poor ability to model ENSO processes), whereas the observational data when summarised as step changes imply a longer term effect on both local and higher-level average temperature curves.

2. The linearity assumption underlying the use of linear regressions for trend analysis of the temperature records is in principle violated by the presence of steps. Thus, the global temperature should not be considered as simply uniformly increasing or accelerating, and claims of average temperature increases and accelerations may be erroneous and misleading. The use of linear regression for analysing temperature (and other climate-related) curves should be reconsidered.

3. Regional and global temperature anomaly curves are “apples and oranges”, as they average over locations differently influenced by natural processes and in different states of the climate system. There is a need to emphasise more on the analysis of local temperature curves.

4. It was recently suggested, that the lack of warming during 1998-2008 was driven largely by natural factors (Kauffmann et al., 2011). Referring to Fig. 1, then what is the explanation for the apparent lack of increase in global temperature during 1977-1986 and 1987-1997? And what is then the conclusion for the overall cause of global warming during 1960-2010?

Finally, I want to make it clear, that I do agree with the presence of an anthropogenic greenhouse effect. But I find reasons in the observational data to doubt, that the IPCC, in its current analysis (AR4, including only data up to 2005), has assessed the relative importance of natural and anthropogenic causes for the temperature changes correctly. The role of natural processes could have been significantly underestimated.

*****************************

My thoughts are that this is a very even handed paper, and properly questions the IPCC. Areas bolded are by me, and important issues brought up in this paper.

[WeatherRusty]

http://wattsupwithth...nso/#more-44897

Implications

It is demonstrated above that the temperature increase in the second half of the 20th century could have taken place in steps driven by major ENSO events. The significance of the finding does not mainly rest on the statistical significance of the model fit, but on the physical support of the ENSO observations for the step changes, identified without making a priori assumptions on the timing or number of steps.

If this was indeed the case – and it could be, unless proven otherwise – then the following implications arise:

1. Natural processes in the ocean-atmosphere system may have had a major influence on the global temperature change in the second half of the 20th century. If so, then something must be wrong with IPCC’s climate models, as the models according to the AR4 can not at all reproduce the observed temperature curve by considering natural causes only. This could question the climate sensitivity of the models and the models ability to adequately describe the natural processes in oceans and atmosphere (eg. ENSO phenomena). While it is generally accepted, that ENSO events can produce abrupt changes in global temperatures, the IPCC considers such effects to be short lived (albeit based on a poor ability to model ENSO processes), whereas the observational data when summarised as step changes imply a longer term effect on both local and higher-level average temperature curves.

2. The linearity assumption underlying the use of linear regressions for trend analysis of the temperature records is in principle violated by the presence of steps. Thus, the global temperature should not be considered as simply uniformly increasing or accelerating, and claims of average temperature increases and accelerations may be erroneous and misleading. The use of linear regression for analysing temperature (and other climate-related) curves should be reconsidered.

3. Regional and global temperature anomaly curves are “apples and oranges”, as they average over locations differently influenced by natural processes and in different states of the climate system. There is a need to emphasise more on the analysis of local temperature curves.

4. It was recently suggested, that the lack of warming during 1998-2008 was driven largely by natural factors (Kauffmann et al., 2011). Referring to Fig. 1, then what is the explanation for the apparent lack of increase in global temperature during 1977-1986 and 1987-1997? And what is then the conclusion for the overall cause of global warming during 1960-2010?

Finally, I want to make it clear, that I do agree with the presence of an anthropogenic greenhouse effect. But I find reasons in the observational data to doubt, that the IPCC, in its current analysis (AR4, including only data up to 2005), has assessed the relative importance of natural and anthropogenic causes for the temperature changes correctly. The role of natural processes could have been significantly underestimated.

*****************************

My thoughts are that this is a very even handed paper, and properly questions the IPCC. Areas bolded are by me, and important issues brought up in this paper.

The idea that ENSO can drive an upward trend in global temperature fails to address a physical mechanism whereby thermal energy is added to the system. In other words, where does the heat come from?

[skierinvermont]

The idea that ENSO can drive an upward trend in global temperature fails to address a physical mechanism whereby thermal energy is added to the system. In other words, where does the heat come from?

It's magic!

Of course global temperature goes up in steps. 2 steps forward 1 step back. That's exactly what IPCC models show. That's exactly what happens when you superimpose natural variability on top of an underlying warming trend. It appears to go up in "steps" but the underlying cause is still CO2.

This article is pretty entertaining to read though.

[tacoman25]

The idea that ENSO can drive an upward trend in global temperature fails to address a physical mechanism whereby thermal energy is added to the system. In other words, where does the heat come from?

How did rapid climate changes happen before? Where did the heat go/come from then? What energy input prompted those changes?

[skierinvermont]

How did rapid climate changes happen before? Where did the heat go/come from then? What energy input prompted those changes?

Which rapid change are you referring to?

[BeastFromTheEast]

Which rapid change are you referring to?

Let's see.. the numerous ice age melts/thaws?

[tacoman25]

Which rapid change are you referring to?

Take your pick. This certainly isn't the first time global temps have changed at least 1C over a couple hundred years.

[skierinvermont]

Take your pick. This certainly isn't the first time global temps have changed at least 1C over a couple hundred years.

First of all, global temperatures have risen .8C in 100 years... not 200.

Second of all, I know of no time when temperatures have risen 1C over a couple hundred years. It might have happened.. it might not of. But we know it hasn't happened in the last 2000 years, and probably not in the last 8000 years.

[skierinvermont]

Let's see.. the numerous ice age melts/thaws?

Took thousands of years to occur and were driven by large changes in radiative forcing (more energy entering the system and/or energy being slower to leave the system).

They were not driven by ENSO which doesn't alter the energy budget of the earth it just moves energy around inside the earth.

[tacoman25]

First of all, global temperatures have risen .8C in 100 years... not 200.

Second of all, I know of no time when temperatures have risen 1C over a couple hundred years. It might have happened.. it might not of. But we know it hasn't happened in the last 2000 years, and probably not in the last 8000 years.

All depends on starting point. If you start in 1910 (a cool point), than yes, about .8C in 100 years. However, if you start earlier in 1880, about .6C in 130 years.

There is no way to have truly accurate global temperature records from thousands of years ago. But there is evidence of rapid warmings in regions where we do have some sort of record...like the Greenland ice core.

[skierinvermont]

There is no way to have truly accurate global temperature records from thousands of years ago. But there is evidence of rapid warmings in regions where we do have some sort of record...like the Greenland ice core.

Scientists believe that we have fairly detailed and accurate reconstructions for the last 2000 years. And that reconstructions for the last 10,000 years are likewise accurate but not quite as detailed on short-term variability.

If you're going to look at regional data (Greenland) then let's make an apples to apples comparison and look at regional data today. We have places that have warmed over 4C in the last 100 years.

Basically, you are willing to believe in historical data showing regional rapid warming.. but not the historical data that takes all of these regional pieces of data and puts them together into something global.

[tacoman25]

Scientists believe that we have fairly detailed and accurate reconstructions for the last 2000 years. And that reconstructions for the last 10,000 years are likewise accurate but not quite as detailed on short-term variability.

If you're going to look at regional data (Greenland) then let's make an apples to apples comparison and look at regional data today. We have places that have warmed over 4C in the last 100 years.

Basically, you are willing to believe in historical data showing regional rapid warming.. but not the historical data that takes all of these regional pieces of data and puts them together into something global.

Where?

I am not saying I "don't believe" global temperature reconstructions. I just doubt how truly accurate they are.

[skierinvermont]

You do realize the GISP2 data you posted above is a regional reconstruction for Greenland right? Just checking.

In response to your question, Egedesminde Greenland has warmed over 4C in the last 60 years alone. It was likely even colder prior to 1950.

[WeatherRusty]

How did rapid climate changes happen before? Where did the heat go/come from then? What energy input prompted those changes?

We are talking global here right? Regionally all that is necessary is a change to the general circulation of either the atmosphere and/or the oceans. Over the eons changes in surface topography and the position of continental masses affect both of these. The type or lack of vegetation is important, for instance prior to 80 million years ago or so there were no grasses covering the surface. Rock weathering rates affect the carbon cycle. The shape of Earth's orbit, angle of axial tilt and the precession of the equinoxes have major impact on climate as will have intrinsic solar output over geologic time frames.

If the global temperature is to change it can only occur due to three factors which affect radiative forcing. This is because all of the energy entering or leaving the Earth is radiative in nature. The three are total integrated solar insolation, the Earth's total outgoing radiation and the Earth's albedo. Anything that affects these three factors can change the radiative balance and thus force Earth's temperature to change.

[tacoman25]

In response to your question, Egedesminde Greenland has warmed over 4C in the last 60 years alone. It was likely even colder prior to 1950.

That is one station in Greenland. Obviously, we don't have records for a single locations dating back thousands of years...but as you can see in the graph I posted above, the Greenland ice core overall saw warmings of several degrees in short periods of time in the past.

[tacoman25]

We are talking global here right? Regionally all that is necessary is a change to the general circulation of either the atmosphere and/or the oceans. Over the eons changes in surface topography and the position of continental masses affect both of these. The type or lack of vegetation is important, for instance prior to 80 million years ago or so there were no grasses covering the surface. Rock weathering rates affect the carbon cycle. The shape of Earth's orbit, angle of axial tilt and the precession of the equinoxes have major impact on climate as will have intrinsic solar output over geologic time frames.

If the global temperature is to change it can only occur due to three factors which affect radiative forcing. This is because all of the energy entering or leaving the Earth is radiative in nature. The three are total integrated solar insolation, the Earth's total outgoing radiation and the Earth's albedo. Anything that affects these three factors can change the radiative balance and thus force Earth's temperature to change.

And these two things have a lot of uncertainty to them and all the mechanism involved are not fully understood by any means.

[BethesdaWX]

That is one station in Greenland. Obviously, we don't have records for a single locations dating back thousands of years...but as you can see in the graph I posted above, the Greenland ice core overall saw warmings of several degrees in short periods of time in the past.

The GISP core is a good representation of the Greenland Climate, and indirectly, the global climate, as the temps there correlate well to multi-century glacial changes, and is well known in science today that the glacier levels right now, globally, are not low compared to those 2-3K years ago.. Obviously Greenland is not going to deviate significantly from the Rest of the Globe on a 500yr+ timescale, as far as change relativity. If Greenland is very warm over a 1000yr timespan, there is little way the globe as a whole cannot be warmer as well, physically, there is no way that in itself is possible based on our knowledge base...and if it were true, the Notion that the warmth in the Arctic is unprecedented within the last 2000yrs is falsified anyway.