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Climate science from climate scientists...

Last Build Date: Tue, 25 Apr 2017 05:04:29 +0000


Comment on Unforced variations: Apr 2017 by David B. Benson

Tue, 25 Apr 2017 05:04:29 +0000

More Clovis Comet evidence? Enigmatic, I opine.

Comment on Unforced variations: Apr 2017 by Generic commenter

Mon, 24 Apr 2017 20:51:00 +0000

Should RealClimate have a readily discoverable photo that shows the thickness of earth's atmosphere? I am having trouble finding it.

Comment on Unforced variations: Apr 2017 by Hank Roberts

Mon, 24 Apr 2017 16:25:10 +0000

Hat tip to Soylent News: [1] A new NASA- and Department of Energy-funded study finds that recent increases in global methane levels observed since 2007 are not necessarily due to increasing emissions, but instead may be due to changes in how long methane remains in the atmosphere after it is emitted. The second most important human-produced greenhouse gas after carbon dioxide, methane is colorless, odorless and can be hard to track. The gas has a wide range of sources, from decomposing biological material to leaks in natural gas pipelines. In the early 2000s, atmospheric scientists studying methane found that its global concentration -- which had increased for decades, driven by methane emissions from fossil fuels and agriculture -- leveled off as the sources of methane reached a balance with its destruction mechanisms. The methane levels remained stable for a few years, then unexpectedly started rising again in 2007, a trend that is still continuing. Previous studies of the renewed increase have focused on high-latitude wetlands or fossil fuels, Asian agricultural growth, or tropical wetlands as potential sources of the increased emissions. But in a study published today in the early online edition of the Proceedings of the National Academy of Sciences, researchers at Harvard University in Cambridge, Massachusetts; Caltech in Pasadena, California; and NASA's Jet Propulsion Laboratory, also in Pasadena, suggest that methane emissions might not have increased dramatically in 2007 after all. [2]Ambiguity in the causes for decadal trends in atmospheric methane and hydroxyl (open, DOI: 10.1073/pnas.1616020114) ([3]DX) Additional reading: [4] ------------------------------------------------------------------------ [5]Original Submission Discuss this story at: Links: 0. 1. 2. 3. 4. 5. +----------------------------------------------------------------------------------------------

Comment on Judy Curry’s attribution non-argument by Frank

Mon, 24 Apr 2017 09:12:09 +0000

Gavin wrote: "Ask yourself one question: Were these models tuned to the observed values? Look at the wonderful agreement between projected and observed warming in Figure SPM-06 from the AR4 SPM. Observations lie right down the middle of projections. Doesn't look anything like the histogram in this post. The appearance of tuning may have come from CMIP3 models. In those models, high climate sensitivity correlated with increasingly negative aerosol forcing. The same thing was not true for CMIP5. Care to show us the histogram for the CMIP3 models or the data that went into SPM-06? Check out Figure 10-05 to see how the use of scaling factors in fingerprinting reduces the tremendous uncertainty in warming due to GHGs and cooling due to aerosols down to little uncertainty in aligning the combined effects of these forcings with observed warming. As best I can tell, fingerprinting assumes that 100% of warming can be attributed to anthropogenic factors. When Judith first questioned the attribution statement, she was looking at Figures like these from the IPCC reports, not histogram you included in this post.

Comment on Judy Curry’s attribution non-argument by MPassey

Mon, 24 Apr 2017 03:10:10 +0000

Gavin, I don’t see from your histogram of CMIP5 simulations vs. temperature trends how it’s “obvious” that the models are not tuned to the initial data. The histogram mode is visually quite close to the temperature data set means. Maybe I’m wrong, but I don’t think Curry is claiming that the models are a simple curve fitting exercise, which would be required for a high precision fit of the models aggregate to the observed data. And you’re not claiming that the models have poor skill at tracking temperature data in the first place, thus proving that they aren’t tuned, right?

[Response: You can't tune the ensemble - only individual models. So if individual models were tuned, they would line up far more closely with the observational trend. That the spread is actually much wider is evidence that they weren't. That the mode of the histogram is quite close is suggests they are (on average) capturing the real forced trend with some variations in internal variability, sensitivity and forcings. - gavin]

Comment on Judy Curry’s attribution non-argument by JCH

Fri, 21 Apr 2017 11:33:32 +0000

I prefer my WfT versions of the PDO and the GMST. Because I was drawing them long before this paper came out: Impact of decadal cloud variations on the Earth’s energy budget From the abstract: ... Specifically, the decadal cloud feedback between the 1980s and 2000s is substantially more negative than the long-term cloud feedback. This is a result of cooling in tropical regions where air descends, relative to warming in tropical ascent regions, which strengthens low-level atmospheric stability. Under these conditions, low-level cloud cover and its reflection of solar radiation increase, despite an increase in global mean surface temperature. These results suggest that sea surface temperature pattern-induced low cloud anomalies could have contributed to the period of reduced warming between 1998 and 2013, and offer a physical explanation of why climate sensitivities estimated from recently observed trends are probably biased low 4. Seen this way, the PDO, whatever the heck it is, lines up quite well throughout.

Comment on Predictable and unpredictable behaviour by Barton Paul Levenson

Fri, 21 Apr 2017 11:01:26 +0000

Mike, you haven't answered my question. Why is the Earth's surface not frozen over? Do you understand why I'm asking this?

Comment on Judy Curry’s attribution non-argument by Barton Paul Levenson

Fri, 21 Apr 2017 10:58:24 +0000

KIA: There can be no quantitative argument proving that AGW exists or doesn’t exist. BPL: Sure there can. You just can't think of one. But your failure of imagination says nothing about what other people can come up with. KIA: we only know the “global” temperature to even a rough degree of certainty for perhaps the past 50 to “maybe” 100 years – an insignificant period in the climate of earth. BPL: Thermometer records go back to the 1600s. Enough for a good estimate of global temperature go back to 1850, which by my calculation is 167 years ago. And for before that, we have proxies. Google "paleoclimatology." KIA: Before that, we have scattered, sparse records using instruments of questionable accuracy BPL: Questionable in what way? KIA: and “stories” of past climate warming and cooling periods. BPL: Not "stories." Inductions based on evidence. You know, the whole "science" thing. KIA: So we can’t even say we have warming today, much less that it is caused by humans. BPL: We have warming today, and it is caused by humans.

Comment on Predictable and unpredictable behaviour by MA Rodger

Fri, 21 Apr 2017 10:56:45 +0000

Mike Flynn @194, Rather than see your unconstrained trolling in this comment thread, can we see what happens when we try a sensible approach to your commenting? You ask us "Do you think I am being unreasonable in wishing to see some experimental support for the supposed GHE?" From past experience, the answer is probably "Yes. It is evident that you are 'being unreasonable'." But let us ignore the past and turn a new leaf. You continue " Nobody can even say why the effect doesn’t seem to work in the dark, indoors, when it’s very cold, or very hot (as in the hottest places on Earth – characterised by a lack of the supposed GHG H2O), or inside a CO2 cylinder, and so on." (My bold) Is what you say correct? Taking the first part of this statement first, why do you say the greenhouse effect "doesn’t seem to work in the dark"?

Comment on Judy Curry’s attribution non-argument by kym horsell

Fri, 21 Apr 2017 09:19:26 +0000

@35 Apparently we need to check the "correlate high frequency components please" box. :) As they say, hypothesis and observation diverge after '85.