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Last Build Date: Mon, 25 Sep 2017 15:54:01 +0000


Comment on Is there really still a chance for staying below 1.5 °C global warming? by Kevin McKinney

Mon, 25 Sep 2017 15:54:01 +0000

Dan H., #47-- "We just need to reduce them to meet the terrestrial removal, which increase with increasing atmospheric concentrations." A dangerous and unwarranted assumption. There is good reason to believe that 'terrestrial removal' could be begin to *reduce* in the future in response to rising temperatures--to note just two cases, conversion of rain forest to savannah in the Amazon, and radical methane emissions increases in the Arctic, due both of melting permafrost and to increasing microbial metabolism.

Comment on Is there really still a chance for staying below 1.5 °C global warming? by Geoff Beacon

Mon, 25 Sep 2017 10:44:07 +0000

Peak temperature arguments imply that bad things happen when global temperatures reach a certain threshold but their severity is independent of the path taken too reach that threshold. Does this imply that a 1.5°C increase in global temperatures brings the same problems independent of the heat stored lower in the oceans or how much the ice caps have melted? Does the emphasis on peak temperature sideline other important measurements? Should we look for other measurements to supplement global temperature targets?

[Response: Good point - the outcome will depend on the path, of course, e.g. for the reasons you give. In practice that is not a big issue, though, since the practical paths from where we are now to stopping global warming at the 1.5 °C level all look very similar. Provided that you assume they are reasonably smooth without abrupt changes to our emissions. -Stefan]

Comment on Is there really still a chance for staying below 1.5 °C global warming? by Gareth S Jones

Mon, 25 Sep 2017 08:52:39 +0000

I think Stefan was somewhat unfair with some of his comments about the HadCRUT4 dataset. The reason the dataset "notoriously [has] a huge data gap in the Arctic." is because, well, there is not a lot of observational data there, especially in the past. HadCRUT4 uses SST measurements from buoys and ships, and land air temperatures from meteorological stations. There is no infilling of data into grid points where there have been no measurements. Saying HadCRUT4 "is not the best data set" relies on assuming that those dataset techniques, that interpolate data into data sparse regions from regions where there is data, do not introduce uncertainties that may influence comparisons with model simulations. We know for instance that the temporal/spatial variability in these in-filled regions is different to where there are observations, which need to be thought about when comparing with model variability. We recently published a paper exploring the impact of observational uncertainty on an attribution analysis. In our discussion exploring the (very minor) differences in results when using different datasets we said:- "Dataset creation approaches that infill missing data areas may give overconfidence to climate changes in regions where there are no direct measurements, when compared with model simulations that have data in those regions." and "care should be taken in the interpretation of data comparisons when using datasets with infilled data areas." There are very good scientific reasons for using observational datasets that fill in data sparse regions in many analyses - I will continue using them - but we should be aware of not only their strengths but also of their weaknesses.

[Response: Hi Gareth, I think the main issue is whether HadCRUT4 is the most appropriate match to true global means in models (as it was effectively used in the Millar paper). An appropriate match to the masked model data would be fine, but is rarely done. One solution which has different assumptions than what is used to define the HadCRUT4 global values, would be to calculate the zonal means first and then area weight those - which assumes that missing data warms at the same rate as the local zonal average as opposed to the global means. Sampling from the reanalyses do suggest that would be more accurate (reduced bias), even if you don't want to go to the Cowtan and Way methodology. - gavin]

Comment on Unforced Variations: Sep 2017 by Killian

Mon, 25 Sep 2017 07:09:15 +0000

A very nice overview of the "100% renewables" fantasy.

Comment on Is there really still a chance for staying below 1.5 °C global warming? by Dan DaSilva

Mon, 25 Sep 2017 05:18:39 +0000

Re 12, Mr. Know It All I also find the use models for predictions with 1/100 degree significant digits to be quite funny.

Comment on Is there really still a chance for staying below 1.5 °C global warming? by Digby Scorgie

Mon, 25 Sep 2017 03:49:40 +0000

Jonathan Richards @31 Scientists first brought the problem to the attention of politicians in 1965. This was when President Johnson was given a comprehensive report on the state of the environment. In the half-century since, the world's politicians have either acknowledged the science and, effectively, done nothing or denied the science and done nothing. What more could the scientists do? The world had been warned; it was up to the politicians to act. It was not the fault of the scientists that the politicians did not act. So I'm not at all surprised that in the intervening years the scientists just continued to do what they knew best: science. They've acquired a greater and greater knowledge and understanding of the planetary climate and accumulated a vast amount of evidence to back them up. In a way, you are correct -- it is irrelevant, but what else could they do? I'm reminded of a story from ancient Japan, where a samurai challenged a tea-master over some slight. The tea-master knew he had no chance against the samurai. Instead, resigned to his fate, he appeared at the appointed time and place with his tea-making paraphernalia and began brewing tea. The samurai relented.

Comment on Unforced Variations: Sep 2017 by John Dailey

Mon, 25 Sep 2017 03:31:24 +0000

Hello, my name is John Dailey, and I had taken Earth Science classes at the University of South Dakota in Vermillion. At that time, what I had learned in those classes had inspired me to create an alternate Earth, with geographic and geological features different from Earth's but still inspired by them. The problem I have is that I know only the Cause--i.e. the changing of the geography--and not the Effect (how the changes in geography influence landscape, climate and weather). I have the whole description written down, but before I show you the description, if it is not too much trouble, would you be willing to help me with feedback and advice on the changes I had made? Thank you for your time.

Comment on Unforced Variations: Sep 2017 by Mal Adapted

Mon, 25 Sep 2017 02:04:49 +0000

That's "coming generations will consume as much energy as they can afford".

Comment on Unforced Variations: Sep 2017 by Mal Adapted

Mon, 25 Sep 2017 01:56:33 +0000

Is the relationship between reduced global population and sustainability linear?
How can it be? Remember I = PAT? Without elaboration, it means that even a shrinking population will exacerbate environmental costs if per-capita consumption rises rapidly enough. Even with rapid build out of a global carbon-neutral economy, multiple other social (including environmental) costs of material prosperity will still be unsustainable. According to The World Bank, global population increased from 3.0 billion in 1960 to 7.4 billion in 2015. Annual per capita energy use grew with population, from about 1.3 tonnes to just under 2.0, roughly proportional to total GHG emissions. In the same period, atmospheric CO2 rose from around 315 to just over 400. Meanwhile, even as lifespans lengthened, estimated global total fertility rate (average number of children a women bears in her life) declined from 5.0 to below 2.5, and is still declining. The current, relatively high annual population growth rate is due to all the women born when TFR was high, whose numerous daughters and granddaughters are on average having fewer daughters of their own. The global replacement TFR, accounting for premenopausal female mortality, is probably not less than 2.3. Demographers thus expect global population to peak between 9 and 12 billion sometime in the next century, before stabilizing and eventually decreasing. The decline in TFR is attributed to improved education for girls, along with female empowerment overall. Like their parents and grandparents, however, coming generations will consume as energy as they can afford at the lowest prices they can find; and they'll be able to afford more than their elders. Consequently, the large-scale anthropogenic transfer of carbon from geologic sequestration to the climatically-active pool will continue as long as fossil fuels are 'cheaper' than carbon-neutral alternatives for substantial numbers of people.

Comment on Unforced Variations: Sep 2017 by Killian

Mon, 25 Sep 2017 01:40:28 +0000

#336 zebra said Prosperity through technology leads to lower birthrates Women having equality, control of births and being educated lowers birth rates, not technology. I think your correlation is spurious. while localized subsistence farming leads to higher ones. Disrupted, degraded, broken cultures might react this way, but intact sustainable cultures tightly control population due to a profound understanding of their environment and the desire to keep it intact. Otherwise, the Amazon, e.g., would have long ago become more densely repopulated. Your correlation is again spurious.