This month’s open thread for climate topics. Please try to stay focused on climate instead of generic (and tedious) political sniping.
Reader Interactions
180 Responses to "Unforced Variations: Apr 2025"
Secular Animistsays
FYI:
“Donald Trump’s administration has dismissed all contributors to the US government’s flagship study on how to prepare for climate change impacts, prompting strong criticism from experts over a ‘senseless’ move. The climate assessment is used by federal and local governments to understand how to prepare for climate crisis impacts including from extreme heat, hurricanes, flooding and drought.
“The dismissal of nearly 400 contributors, who are scientists and other experts, to the sixth National Climate Assessment (NCA), which is mandated by Congress, leaves the future of the report in doubt since the multi-year, peer-reviewed analysis is due for publication in 2028.”
This was predicted to happen long ago now, and far more accurately (imo) than the GCM models operate.
In fact it should have been expected to be just like this. I mean seriously SA, what else did you expect would happen given the last 30-40 years of American style politics and the values Americans actually cherish as gospel — as opposed to the usual lip service ?
Poor America. Maybe now the RoW will ostracize you completely as a nation. That more than anything else will improve actions to reduce the harmful effects of climate change now upon us.
Another month draws to a close allowing another monthly dot to be plotted on the global temperature record.
The daily ERA5 numbers at Climate Pulse show April’s SAT averaging +0.60ºC, down on previous months of 2025-so-far (Jan +0.79ºC, Feb +0.63ºC, Mar +0.66ºC) with Jan-Apr2025 (+0.67ºC) also lower than Jan-Apr2024 (+0.73ºC). (A plot of the daily numbers sequenced 2022-to-date is posted here – First POSTED 17th March 2025.)
This 2024-2025 comparison is what James Hansen considers to be the “acid” test for his proposal that the “bananas” temperatures of late 2023-into-2024 were “due about equally to a moderate El Nino and reduction of ship aerosols, with a smaller contribution from the present solar maximum.” Thus:-
An “acid” test of our interpretation will be provided by the 2025 global temperature: unlike the 1997-98 and 2015-16 El Ninos, which were followed by global cooling of more than 0.3°C and 0.2°C, respectively, we expect global temperature in 2025 to remain near or above the 1.5°C level. Indeed, the 2025 might even set a new record despite the present weak La Nina.
The Jan-Apr averages using the same anomaly base as Hansen’s “1.5°C level” (1850-1900 base) run 2023 +1.29°C, 2024 +1.67°C, 2025 +1.61°C. (** The ENSO looks like its stuck on neutral for the year. Up-to-date, April’s NINO3.4 sits at -0.1ºC.)
While I am not myself convinced of Hansen’s proposed role of “reduction of ship aerosols,” I would suggest that the wibbly-wobbly global SAT is not the best data to use for this “acid test” and would suggest the 60N-60S SST (also provided by Climate Pulse) gives a better indication. That SST shows things without such large wobbles and is thus showing the level of 2025 cooling more clearly.
Thus, while the April SAT over the last 3 years run 2023 +0.32ºC, 2024 +0.67ºC, 2025 +0.60ºC (1850-1900 base +1.23°C,+1.58°C * +1.51°C), this is not very clear as to where 2025 is progressing.
Using the SST does have the wrinkle that the SST anomalies don’t readily translate to an 1850-1900 base and if it did the “1.5°C level” wouldn’t apply. But that said,the 60N-60S SST is a lot easier to meaningfully ‘eyeball’ at Climate Pulse. This shows SSTs still struggling to dip below the +0.4ºC but also it is still managing to show slow-but-on-going cooling. Thus comparing Apr2025 with previous year – 2025 +0.39ºC, 2024 +0.54ºC & 2023 +0.36ºC. And note this last 2023 anomaly would have been subject to AGW of +0.03ºC in the following 2 years although there is a strong “bananas” flavour arriving by April 2023. I would thus suggest as a better “acid test”, that 60-60 SST dropping towards +0.3ºC by the year’s-end. This measure would at least avoid objections to the 1988 & 2016 SAT comparisons having to negotiate these earlier El Niño years showing their peak temperatures respectively 8-months and 4-months later than their 2024 counterpart.
Mind, I would still not see even that “acid test” convincing me that there was a big “reduction of ship aerosols” in the “bananas.” (I should explain why.)
Secular Animistsays
FYI: For those who don’t already know of it, this looks like a useful website:
“ClimaMeter is a rapid experimental framework for putting weather extremes in a climate perspective, developed by the ESTIMR team at the Laboratoire des Sciences du Climat et de l’Environnement (Institut Pierre Simon Laplace) in Paris-Saclay. ClimaMeter is led by Davide Faranda (CNRS & London Mathematical Laboratory), Mathieu Vrac (CNRS), Pascal Yiou (CEA-Saclay) & Robert Vautard (IPSL), in collaboration with Gabriele Messori (Uppsala University, Uppsala), Erika Coppola (International Centre for Theoretical Physics, Trieste) and Tommaso Alberti (Istituto Nazionale di Geofisica e Vulcanologia, Rome).
“We provide an easily interpretable contextualisation of extreme weather immediately after the actual event, as well as a more technical description and discussion of the event with a slightly longer delay.”
For MAY: a follow up backgrounder about the Iberian blackout 1of2
Germany’s energy transition, initiated by Angela Merkel’s government in 2011 and aimed at shifting the country’s power supply to primarily wind and solar energy, is facing mounting challenges. Despite a record expansion of renewable infrastructure, electricity production from renewables in the first quarter of 2025 dropped 16% compared to the previous year—the lowest output since 2021. Particularly weak wind conditions in February and March caused offshore wind production to plummet by 31% and onshore by 22%. As a result, Germany was forced to ramp up power generation from coal, oil, and gas, significantly increasing CO₂ emissions. The country’s electricity became dirtier than at any point since the winter of 2018, contradicting the goals of the energy transition.
These issues came to a head during Easter week, which showcased the structural flaws in Germany’s reliance on weather-dependent renewables. On Easter Sunday, solar panels produced a massive oversupply of electricity—about 15 gigawatts more than needed, equivalent to the output of a dozen nuclear power plants. Since electricity must be consumed as it is generated, this surplus overwhelmed local and regional grids, especially in southwestern Germany. The excess led to negative electricity prices, with rates falling as low as -5 cents per kilowatt-hour. Germany even had to pay neighboring countries like France and Belgium to absorb the surplus in order to prevent a grid collapse.
The most critical issue is that Germany’s vast network of solar installations cannot be easily regulated or disconnected when generation exceeds demand. This inability to curtail production during peak generation periods not only risks grid instability and localized outages, but also inflates the overall cost of power production. The Easter scenario starkly illustrated how the current model of the energy transition—despite its ambitions—can create vulnerabilities that contradict its environmental and economic objectives.
Poor Perusays
For May- backgrounder 2of2
The recent ten-hour utility blackout across the Iberian Peninsula highlights a growing vulnerability within Europe’s energy infrastructure—not just in terms of power generation, but more critically, in the transmission of electricity. While weather likely played a role in the outage, it also exposes a broader issue affecting renewable-heavy countries like Germany and Spain: intermittent supply, outdated grids, and overproduction.
Germany has become Europe’s largest CO₂ emitter, not because of a lack of renewables, but due to the need to rely on coal during periods when solar and wind production dip—especially in the absence of Russian gas and decommissioned nuclear power. Similarly, Spain and Portugal, hailed as EU leaders in green energy, were sourcing 80% of their electricity from renewables just before the blackout. Yet both regions are now confronting the harsh reality that overproduction from wind and solar, without adequate grid infrastructure, can destabilize entire systems.
A major flaw lies in Europe’s aging electrical grid, much of which was built in the post-war 1950s and 60s and never designed to handle the variable and decentralized nature of modern renewable sources. While Angela Merkel’s government once promised thousands of kilometers of new “electricity highways” (Strom Autobahnen) as part of the Energiewende, the promised budget of one trillion euros was never established. As a result, the critical grid expansion never materialized—neither in Germany nor in other EU states.
This infrastructure gap is now colliding with the electrification push, particularly in mobility. Electric vehicle adoption is slowing as consumer enthusiasm wanes, but the underlying strain on the grid remains. Europe’s Continental European Synchronous Area—a vast network extending from Türkiye to North Africa—runs on a finely balanced alternating current of about 50 Hz. Any overload, such as Monday’s in Spain, risks frequency destabilization. To prevent blackouts, surplus energy is exported, but insufficient interconnectors—or too many—can both trigger wider instability. Some experts now fear that adding more interconnectors could actually increase the likelihood of continent-wide domino blackouts across 30+ countries.
Ultimately, the ambition of green energy must be matched with realistic investment in transmission capacity and a well-timed rollout. Without this, Europe’s green dreams may keep short-circuiting under pressure.
FYI:
“Donald Trump’s administration has dismissed all contributors to the US government’s flagship study on how to prepare for climate change impacts, prompting strong criticism from experts over a ‘senseless’ move. The climate assessment is used by federal and local governments to understand how to prepare for climate crisis impacts including from extreme heat, hurricanes, flooding and drought.
“The dismissal of nearly 400 contributors, who are scientists and other experts, to the sixth National Climate Assessment (NCA), which is mandated by Congress, leaves the future of the report in doubt since the multi-year, peer-reviewed analysis is due for publication in 2028.”
https://www.theguardian.com/us-news/2025/apr/29/trump-fires-climate-report-contributors
This was predicted to happen long ago now, and far more accurately (imo) than the GCM models operate.
In fact it should have been expected to be just like this. I mean seriously SA, what else did you expect would happen given the last 30-40 years of American style politics and the values Americans actually cherish as gospel — as opposed to the usual lip service ?
Poor America. Maybe now the RoW will ostracize you completely as a nation. That more than anything else will improve actions to reduce the harmful effects of climate change now upon us.
Another example of Trump’s war on the common good, and specifically meaningful climate action.
But Poor Peru comforts us that “it doesn’t matter.” I feel so much better now!
Another month draws to a close allowing another monthly dot to be plotted on the global temperature record.
The daily ERA5 numbers at Climate Pulse show April’s SAT averaging +0.60ºC, down on previous months of 2025-so-far (Jan +0.79ºC, Feb +0.63ºC, Mar +0.66ºC) with Jan-Apr2025 (+0.67ºC) also lower than Jan-Apr2024 (+0.73ºC). (A plot of the daily numbers sequenced 2022-to-date is posted here – First POSTED 17th March 2025.)
This 2024-2025 comparison is what James Hansen considers to be the “acid” test for his proposal that the “bananas” temperatures of late 2023-into-2024 were “due about equally to a moderate El Nino and reduction of ship aerosols, with a smaller contribution from the present solar maximum.” Thus:-
The Jan-Apr averages using the same anomaly base as Hansen’s “1.5°C level” (1850-1900 base) run 2023 +1.29°C, 2024 +1.67°C, 2025 +1.61°C. (** The ENSO looks like its stuck on neutral for the year. Up-to-date, April’s NINO3.4 sits at -0.1ºC.)
While I am not myself convinced of Hansen’s proposed role of “reduction of ship aerosols,” I would suggest that the wibbly-wobbly global SAT is not the best data to use for this “acid test” and would suggest the 60N-60S SST (also provided by Climate Pulse) gives a better indication. That SST shows things without such large wobbles and is thus showing the level of 2025 cooling more clearly.
Thus, while the April SAT over the last 3 years run 2023 +0.32ºC, 2024 +0.67ºC, 2025 +0.60ºC (1850-1900 base +1.23°C,+1.58°C * +1.51°C), this is not very clear as to where 2025 is progressing.
Using the SST does have the wrinkle that the SST anomalies don’t readily translate to an 1850-1900 base and if it did the “1.5°C level” wouldn’t apply. But that said,the 60N-60S SST is a lot easier to meaningfully ‘eyeball’ at Climate Pulse. This shows SSTs still struggling to dip below the +0.4ºC but also it is still managing to show slow-but-on-going cooling. Thus comparing Apr2025 with previous year – 2025 +0.39ºC, 2024 +0.54ºC & 2023 +0.36ºC. And note this last 2023 anomaly would have been subject to AGW of +0.03ºC in the following 2 years although there is a strong “bananas” flavour arriving by April 2023. I would thus suggest as a better “acid test”, that 60-60 SST dropping towards +0.3ºC by the year’s-end. This measure would at least avoid objections to the 1988 & 2016 SAT comparisons having to negotiate these earlier El Niño years showing their peak temperatures respectively 8-months and 4-months later than their 2024 counterpart.
Mind, I would still not see even that “acid test” convincing me that there was a big “reduction of ship aerosols” in the “bananas.” (I should explain why.)
FYI: For those who don’t already know of it, this looks like a useful website:
“ClimaMeter is a rapid experimental framework for putting weather extremes in a climate perspective, developed by the ESTIMR team at the Laboratoire des Sciences du Climat et de l’Environnement (Institut Pierre Simon Laplace) in Paris-Saclay. ClimaMeter is led by Davide Faranda (CNRS & London Mathematical Laboratory), Mathieu Vrac (CNRS), Pascal Yiou (CEA-Saclay) & Robert Vautard (IPSL), in collaboration with Gabriele Messori (Uppsala University, Uppsala), Erika Coppola (International Centre for Theoretical Physics, Trieste) and Tommaso Alberti (Istituto Nazionale di Geofisica e Vulcanologia, Rome).
“We provide an easily interpretable contextualisation of extreme weather immediately after the actual event, as well as a more technical description and discussion of the event with a slightly longer delay.”
https://www.climameter.org/home
For MAY: a follow up backgrounder about the Iberian blackout 1of2
Germany’s energy transition, initiated by Angela Merkel’s government in 2011 and aimed at shifting the country’s power supply to primarily wind and solar energy, is facing mounting challenges. Despite a record expansion of renewable infrastructure, electricity production from renewables in the first quarter of 2025 dropped 16% compared to the previous year—the lowest output since 2021. Particularly weak wind conditions in February and March caused offshore wind production to plummet by 31% and onshore by 22%. As a result, Germany was forced to ramp up power generation from coal, oil, and gas, significantly increasing CO₂ emissions. The country’s electricity became dirtier than at any point since the winter of 2018, contradicting the goals of the energy transition.
These issues came to a head during Easter week, which showcased the structural flaws in Germany’s reliance on weather-dependent renewables. On Easter Sunday, solar panels produced a massive oversupply of electricity—about 15 gigawatts more than needed, equivalent to the output of a dozen nuclear power plants. Since electricity must be consumed as it is generated, this surplus overwhelmed local and regional grids, especially in southwestern Germany. The excess led to negative electricity prices, with rates falling as low as -5 cents per kilowatt-hour. Germany even had to pay neighboring countries like France and Belgium to absorb the surplus in order to prevent a grid collapse.
The most critical issue is that Germany’s vast network of solar installations cannot be easily regulated or disconnected when generation exceeds demand. This inability to curtail production during peak generation periods not only risks grid instability and localized outages, but also inflates the overall cost of power production. The Easter scenario starkly illustrated how the current model of the energy transition—despite its ambitions—can create vulnerabilities that contradict its environmental and economic objectives.
For May- backgrounder 2of2
The recent ten-hour utility blackout across the Iberian Peninsula highlights a growing vulnerability within Europe’s energy infrastructure—not just in terms of power generation, but more critically, in the transmission of electricity. While weather likely played a role in the outage, it also exposes a broader issue affecting renewable-heavy countries like Germany and Spain: intermittent supply, outdated grids, and overproduction.
Germany has become Europe’s largest CO₂ emitter, not because of a lack of renewables, but due to the need to rely on coal during periods when solar and wind production dip—especially in the absence of Russian gas and decommissioned nuclear power. Similarly, Spain and Portugal, hailed as EU leaders in green energy, were sourcing 80% of their electricity from renewables just before the blackout. Yet both regions are now confronting the harsh reality that overproduction from wind and solar, without adequate grid infrastructure, can destabilize entire systems.
A major flaw lies in Europe’s aging electrical grid, much of which was built in the post-war 1950s and 60s and never designed to handle the variable and decentralized nature of modern renewable sources. While Angela Merkel’s government once promised thousands of kilometers of new “electricity highways” (Strom Autobahnen) as part of the Energiewende, the promised budget of one trillion euros was never established. As a result, the critical grid expansion never materialized—neither in Germany nor in other EU states.
This infrastructure gap is now colliding with the electrification push, particularly in mobility. Electric vehicle adoption is slowing as consumer enthusiasm wanes, but the underlying strain on the grid remains. Europe’s Continental European Synchronous Area—a vast network extending from Türkiye to North Africa—runs on a finely balanced alternating current of about 50 Hz. Any overload, such as Monday’s in Spain, risks frequency destabilization. To prevent blackouts, surplus energy is exported, but insufficient interconnectors—or too many—can both trigger wider instability. Some experts now fear that adding more interconnectors could actually increase the likelihood of continent-wide domino blackouts across 30+ countries.
Ultimately, the ambition of green energy must be matched with realistic investment in transmission capacity and a well-timed rollout. Without this, Europe’s green dreams may keep short-circuiting under pressure.