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The NASA data conspiracy theory and the cold sun

When climate deniers are desperate because the measurements don’t fit their claims, some of them take the final straw: they try to deny and discredit the data.

The years 2014 and 2015 reached new records in the global temperature, and 2016 has done so again. Some don’t like this because it doesn’t fit their political message, so they try to spread doubt about the observational records of global surface temperatures. A favorite target are the adjustments that occur as these observational records are gradually being vetted and improved by adding new data and eliminating artifacts that arise e.g. from changing measurement practices or the urban heat island effect. More about this is explained in this blog article by Victor Venema from Bonn University, a leading expert on homogenization of climate data. And of course the new paper by Hausfather et al, that made quite a bit of news recently, documents how meticulously scientists work to eliminate bias in sea surface temperature data, in this case arising from a changing proportion of ship versus buoy observations. More »

The underestimated danger of a breakdown of the Gulf Stream System

Filed under: — stefan @ 4 January 2017

A new model simulation of the Gulf Stream System shows a breakdown of the gigantic overturning circulating in the Atlantic after a CO2 doubling.

A new study in Science Advances by Wei Liu and colleagues at the Scripps Institution of Oceanography in San Diego and the University of Wisconsin-Madison has important implications for the future stability of the overturning circulation in the Atlantic Ocean. They applied a correction to the freshwater fluxes in the Atlantic, in order to better reproduce the salt concentration of ocean waters there. This correction changes the overall salt budget for the Atlantic, also changing the stability of the model’s ocean circulation in future climate change. The Atlantic ocean circulation is relatively stable in the uncorrected model, only declining by about 20% in response to a CO2 doubling, but in the corrected model version it breaks down completely in the centuries following a CO2 doubling, with dramatic consequences for the climate of the Northern Hemisphere. More »

Record heat despite a cold sun

Filed under: — stefan @ 14 November 2016

Global temperature goes from heat record to heat record, yet the sun is at its dimmest for half a century.

For a while, 2010 was the hottest year on record globally. But then it got overtopped by 2014. And 2014 was beaten again by 2015. And now 2016 is so warm that it is certain to be once again a record year. Three record years in a row – that is unprecedented even in all those decades of global warming.

Strangely, one aspect of this gets barely mentioned: all those heat records occur despite a cold sun (Figs. 1 and 2). The last solar minimum (2008-2010) was the lowest since at least 1950, while the last solar maximum (2013-2015) can hardly be described as such. This is shown, among others, by the sunspot data (Fig. 1) as well as measurements of the solar luminosity from satellites (Fig. 2). Other indicators of solar activity indicate cooling as well (Lockwood and Fröhlich, Proc. Royal Society 2007).


Fig. 1 Time evolution of global temperature, CO2 concentration and solar activity. Temperature and CO2 are scaled relative to each other according to the physically expected CO2 effect on climate (i.e. the best estimate of transient climate sensitivity). The amplitude of the solar curve is scaled to correspond to the observed correlation of solar and temperature data. (Details are explained here.) You can generate and adapt this graph to your taste here, where you can also copy a code with which the graph can be embedded as a widget on your own website (as on my home page). Thus it will be automatically updated each year with the latest data. Thanks to our reader Bernd Herd who programmed this. More »

Q & A about the Gulf Stream System slowdown and the Atlantic ‘cold blob’

Last weekend, in Reykjavik the Arctic Circle Assembly was held, the large annual conference on all aspects of the Arctic. A topic of this year was: What’s going on in the North Atlantic? This referred to the conspicuous ‘cold blob’ in the subpolar Atlantic, on which there were lectures and a panel discussion (Reykjavik University had invited me to give one of the talks). Here I want to provide a brief overview of the issues discussed.

What is the ‘cold blob’?

This refers to exceptionally cold water in the subpolar Atlantic south of Greenland. In our paper last year we have shown it like this (see also our RealClimate post about it):


Fig. 1 Linear temperature trends from 1901 to 2013 according to NASA data. Source: Rahmstorf et al, Nature Climate Change 2015.

More »

Can a blanket violate the second law of thermodynamics?

Filed under: — stefan @ 20 September 2016

One of the silliest arguments of climate deniers goes like this: the atmosphere with its greenhouse gases cannot warm the Earth’s surface, because it is colder than the surface. But heat always flows from warm to cold and never vice versa, as stated in the second law of thermodynamics.

The freshly baked Australian Senator Malcolm Roberts has recently phrased it thus in his maiden speech:

It is basic. The sun warms the earth’s surface. The surface, by contact, warms the moving, circulating atmosphere. That means the atmosphere cools the surface. How then can the atmosphere warm it? It cannot. That is why their computer models are wrong.

This is of course not only questions the increasing human-caused greenhouse effect, but in general our understanding of temperatures on all planets, which goes back to Joseph Fourier, who in 1824 was the first to understand the importance of the greenhouse effect.

The atmosphere acts like a blanket which inhibits heat loss. In fact according to Roberts’ logic, a blanket could also not have a warming effect:

It’s simple. The body warms the blanket. This means that the blanket cools the body. So how can the blanket warm it? It cannot!

The answer is simple. The warm body loses heat to the cold air. The blanket inhibits and slows this heat loss. Therefore you stay warmer under a blanket.

The Earth loses heat to the cold universe. The atmosphere inhibits this heat loss. Therefore, the surface remains warmer than it would be without the atmosphere.

It is true that the surface loses heat to the atmosphere – but less than it would otherwise lose directly to space. Just as I lose less heat to the blanket than I would otherwise lose to the air, without blanket.

Of course, in neither case is the second law of thermodynamics violated. The heat always flows from warm to cold – just more or less effectively. The processes of heat transfer are quite different – for the blanket it is mainly heat conduction, for the greenhouse effect it is thermal radiation. The climate deniers claim that the colder atmosphere cannot radiate thermal radiation towards the warmer surface. This is of course nonsense. The cool Earth also sends thermal radiation towards the hot sun – how would thermal radiation leaving Earth know how warm the surface is that it’s going to hit? It’s just that the sun sends more radiation back to us  – the net flow is from hot to cold. More is not implied by the second law of thermodynamics.

Thanks to two Germans (Gerlich and Tscheuschner of the TU Braunscheig – deeply embarrassing for this university), the absurd claim that the greenhouse effect violates the second law of thermodynamics even made it into an obscure physics journal – obviously there was no peer review to speak of. The bizarre article was promptly demolished by some US physicists. Just recently I read the claim again in an article of coal lobbyist Lars Schernikau – with such fairy-tale beliefs of its representatives, one is not surprised by the decline of the coal industry.

The thermal radiation from the atmosphere toward the ground, which allegedly cannot exist, is of course routinely measured, including its increase (see e.g. Philipona et al. 2004, 2012).

And you can even feel it. Those who sometimes sit outside in the garden after dark know this. Under a dense, low cloud layer you do not nearly get cold as fast as on a clear starry night. This is due to the thermal radiation coming from the clouds. They are colder than our body, but warmer than the night sky in clear air.

Roberts said: “Like Socrates, I love asking questions to get to the truth.”  Perhaps he will ponder my answer next time he sits in his garden at night, or slips under a blanket.


Here is the energy balance diagram for our Earth, explained in IPCC FAQ 1.1. The “Back Radiation” makes the greenhouse effect. It is larger than the solar radiation reaching the ground, and measured by a global radiation measurement network.



R. Philipona, “Radiative forcing – measured at Earth’s surface – corroborate the increasing greenhouse effect”, Geophys. Res. Lett., vol. 31, 2004.

R. Philipona, A. Kräuchi, and E. Brocard, “Solar and thermal radiation profiles and radiative forcing measured through the atmosphere”, Geophys. Res. Lett., vol. 39, pp. n/a-n/a, 2012.

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