Prof. Stefan RahmstorfNuclear #fusion will not only come too late to help solve the #climatecrisis. Even in the long run it will not be the unlimited energy source that some are dreaming of. The reason is basic physics, and anyone can do the back-of-envelope calculation. đ§”1/
The problem is that all human energy use ends up as heat. That's no problem now: our current global energy use corresponds to 0.04 Watt/sqm (that's per square metre of Earth surface). The human-caused CO2 increase has a far stronger warming effect: 2.1 W/sqm, following IPCC. 2/
But our energy use (here also in W/sqm) is growing exponentially by 2.3 %/year, 10-fold per century. What does this mean for the future? The Master thesis by Peter Steiglechner @PIK_Climate investigated this in 2018 using a global climate model. Figures taken from his work. 3/
But first, back of envelope: a 10-fold increase in energy use from the current results in a heat flux of 0.4 W/sqm.
With the standard IPCC climate sensitivity that results in 0.3 °C global warming. Oops, now this is a problem, coming on top of greenhouse warming! 4/
With the standard IPCC climate sensitivity that results in 0.3 °C global warming. Oops, now this is a problem, coming on top of greenhouse warming! 4/
Here's two scenarios to 2100 Peter studied (black lines): 2% increase per year, and a more moderate IPCC scenario called SSP5. Thatâs less than a ten-fold increase. BUT: the heat release is not globally uniform. Unlike for CO2, it is concentrated where we live, on land. 5/
That is why the (admittedly rather coarse) climate model shows warming concentrated over Northern Hemisphere land, reaching 0.2 â 0.4 °C warming there by 2100 (not even yet in equilibrium). And weâre already struggling to prevent every 0.1 °C of further warming! /6
In terms of heat release, nuclear power (fusion or fission) is just as bad as coal.
Renewables are different: they use energy from wind, sun, tides or geothermal which is already in the climate system and will end up as heat anyway, whether we use it or not. /7
Renewables are different: they use energy from wind, sun, tides or geothermal which is already in the climate system and will end up as heat anyway, whether we use it or not. /7
(In case you want to say now: but extra heat is radiated into space! This is of course already taken into account. The Earth must get warmer to radiate more, that is what the climate sensitivity describes.) /8
The bottom line is: if humanity wants to use a lot more energy in future, nuclear power can't be the solution. Not just not for the next decades, but also in the long run renewable energies are the only sustainable solution. /9
These technologies we already have, they are growing exponentially and are safe and cheap. (And don't tell me the sun doesn't shine at night - energy system experts already account for that, believe it or not.) /10
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RT @scienceisstrat1
The @IEAâs bombshell new report on renewables has incredibly good news.
For example, solar is undergoing a mega boom & may surpass coal by 2027
Below is a 𧔠on genuinely good news on green enerâŠ
https://twitter.com/scienceisstrat1/status/1601650724852895744
Science Is Strategic on Twitter
âThe @IEAâs bombshell new report on renewables has incredibly good news. For example, solar is undergoing a mega boom & may surpass coal by 2027 Below is a 𧔠on genuinely good news on green energy from the IEA & beyond (1/22) Cc: @Noahpinion @JesseJenkins @ramez @dwallacewellsâ
A similar argument regarding waste heat was recently made in a peer-reviewed paper in Nature Physics as well. Check it out if you like. /11
https://www.nature.com/articles/s41567-022-01652-6
https://www.nature.com/articles/s41567-022-01652-6
Link to the Master thesis of Peter Steiglechner: https://publishup.uni-potsdam.de/frontdoor/index/index/docId/49886
publish.UP Estimating global warming from anthropogenic heat emissions
The forcing from the anthropogenic heat flux (AHF), i.e. the dissipation of primary energy consumed by the human civilisation, produces a direct climate warming. Today, the globally averaged AHF is negligibly small compared to the indirect forcing from greenhouse gas emissions. Locally or regionally, though, it has a significant impact. Historical observations show a constant exponential growth of worldwide energy production. A continuation of this trend might be fueled or even amplified by the exploration of new carbon-free energy sources like fusion power. In such a scenario, the impacts of the AHF become a relevant factor for anthropogenic post-greenhouse gas climate change on the global scale, as well. This master thesis aims at estimating the climate impacts of such a growing AHF forcing. In the first part of this work, the AHF is built into simple and conceptual, zero- and one-dimensional Energy Balance Models (EBMs), providing quick order of magnitude estimations of the temperature impact. In the one-dimensional EBM, the ice-albedo feedback from enhanced ice melting due to the AHF increases the temperature impact significantly compared to the zero-dimensional EBM. Additionally, the forcing is built into a climate model of intermediate complexity, CLIMBER-3α. This allows for the investigation of the effect of localised AHF and gives further insights into the impact of the AHF on processes like the ocean heat uptake, sea ice and snow pattern changes and the ocean circulation. The global mean temperature response from the AHF today is of the order of 0.010 â 0.016 K in all reasonable model configurations tested. A transient tenfold increase of this forcing heats up the Earth System additionally by roughly 0.1 â 0.2 K in the presented models. Further growth can also affect the tipping probability of certain climate elements. Most renewable energy sources do not or only partially contribute to the AHF forcing as the energy from these sources dissipates anyway. Hence, the transition to a (carbon-free) renewable energy mix, which, in particular, does not rely on nuclear power, eliminates the local and global climate impacts from the increasing AHF forcing, independent of the growth of energy production.
Bernhard Klingseis@rahmstorf thank you for sharing! So if I understood right we could at least have some nuclear fusion reactors on some remote islands to capture some GHG, right?
Someone brought up the energy expended in building the plant, incl. mining. For wind power thatâs at most a few % of the electricity generated - in this example under 1% for 20y turbine life. Nuclear plants add 300% of the generated power as heat to the đ at 33% efficiency.
Arco@rahmstorf This calculation seems wrong to me:
- 33% efficiency, means 67% heat loss
- 67% heat loss â 200% of the generated power
- 33% efficiency, means 67% heat loss
- 67% heat loss â 200% of the generated power
Wolfgang Maier@Arco @rahmstorf I'm assuming 300% is because the generated power will end up as heat, too.
@zerodivision @rahmstorf Ah in that case ok, but the formulation sounded weird to me ^^
Ariaflame@Arco @rahmstorf Except of course that eventually all that generated power will also degrade to heat energy. Laws of thermodynamics.
MichaĆ Kawalec@rahmstorf Does the energy emitted as heat really matter, except for maybe local effects related to availability of the cooling water? Different kinds of non-carbon energy production methods have different usefulness profiles.
Dienstreiser Jens@rahmstorf Just read the related chapter in the book #WeltuntergangFĂ€lltAus from @JanHegenberg.
it's remarkable how much more Power you can generate with a wind turbine, compared to a coal plant with the same amount of minerals mined from the ground.
it's remarkable how much more Power you can generate with a wind turbine, compared to a coal plant with the same amount of minerals mined from the ground.