Robert Rohde
@rarohde.bsky.social
Chief Scientist for @berkeleyearth.org.
Physics PhD & data nerd. Usually focused on climate change, fossil fuels, & air quality issues.
Physics PhD & data nerd. Usually focused on climate change, fossil fuels, & air quality issues.
Pinned
Robert Rohde
@rarohde.bsky.social
· Nov 22
Early-twentieth-century cold bias in ocean surface temperature observations - Nature
Independent statistical reconstructions of the global mean surface temperature from either ocean or land data show that existing estimates of early-twentieth-century ocean surface temperatures are too...
www.nature.com
A new paper led by Sebastian Sippel just appeared in Nature arguing that ocean temperature measurements in the early 20th century have a cold bias.
It's a fun story illustrating the process of scientific discovery, so let me talk about it a bit. 🧵
www.nature.com/articles/s41...
It's a fun story illustrating the process of scientific discovery, so let me talk about it a bit. 🧵
www.nature.com/articles/s41...
Reposted by Robert Rohde
Excellent @washingtonpost.com piece on the signs that global warming is accelerating by @shannonosaka.bsky.social and @johnmuyskens.bsky.social, featuring @hausfath.bsky.social @rarohde.bsky.social @cjsmith.eu
www.washingtonpost.com/climate-envi...
www.washingtonpost.com/climate-envi...
February 11, 2026 at 10:26 PM
Excellent @washingtonpost.com piece on the signs that global warming is accelerating by @shannonosaka.bsky.social and @johnmuyskens.bsky.social, featuring @hausfath.bsky.social @rarohde.bsky.social @cjsmith.eu
www.washingtonpost.com/climate-envi...
www.washingtonpost.com/climate-envi...
Reposted by Robert Rohde
New discussion paper just dropped that’s taken shall we say a little work to get this far … essd.copernicus.org/preprints/es... please be kind. Not on an at all sensitive topic in the slightest.
How well can we quantify when 1.5 °C of global warming has been exceeded?
Abstract. Parties to the 2015 Paris Agreement agreed to limit the long-term increase in global average temperature to well below 2 °C and pursue efforts to keep temperatures below 1.5 °C relative to p...
essd.copernicus.org
January 28, 2026 at 8:48 AM
New discussion paper just dropped that’s taken shall we say a little work to get this far … essd.copernicus.org/preprints/es... please be kind. Not on an at all sensitive topic in the slightest.
I'm not really sure. Obviously it depends on precise, well-calibrated, robust, and stable radiometers in space, and ideally several at the same time for cross-validation.
But I'm not close enough to say what the remaining key technical challenges are.
But I'm not close enough to say what the remaining key technical challenges are.
January 23, 2026 at 9:28 AM
I'm not really sure. Obviously it depends on precise, well-calibrated, robust, and stable radiometers in space, and ideally several at the same time for cross-validation.
But I'm not close enough to say what the remaining key technical challenges are.
But I'm not close enough to say what the remaining key technical challenges are.
Now, forcings due to additional greenhouse gases are clearly larger than the observed solar changes.
But total solar irradiance remains a pretty important boundary condition for all climate and climate change work.
One would think that we would have solar variation nailed down better by now.
But total solar irradiance remains a pretty important boundary condition for all climate and climate change work.
One would think that we would have solar variation nailed down better by now.
January 22, 2026 at 10:35 AM
Now, forcings due to additional greenhouse gases are clearly larger than the observed solar changes.
But total solar irradiance remains a pretty important boundary condition for all climate and climate change work.
One would think that we would have solar variation nailed down better by now.
But total solar irradiance remains a pretty important boundary condition for all climate and climate change work.
One would think that we would have solar variation nailed down better by now.
I understand why it is hard.
Total solar irradiance is ~1361 W/m², so measuring a ~1 W/m² change is less than a 0.1% change.
And it can only be done with satellites, which often degrade and get replaced, requiring the synthesis of many (sometimes inconsistent) measurements.
Total solar irradiance is ~1361 W/m², so measuring a ~1 W/m² change is less than a 0.1% change.
And it can only be done with satellites, which often degrade and get replaced, requiring the synthesis of many (sometimes inconsistent) measurements.
January 22, 2026 at 10:35 AM
I understand why it is hard.
Total solar irradiance is ~1361 W/m², so measuring a ~1 W/m² change is less than a 0.1% change.
And it can only be done with satellites, which often degrade and get replaced, requiring the synthesis of many (sometimes inconsistent) measurements.
Total solar irradiance is ~1361 W/m², so measuring a ~1 W/m² change is less than a 0.1% change.
And it can only be done with satellites, which often degrade and get replaced, requiring the synthesis of many (sometimes inconsistent) measurements.
It is wild to me that in 2025 the question of how much does solar output change during a solar cycle still comes with a ~20% measurement uncertainty.
January 22, 2026 at 10:32 AM
It is wild to me that in 2025 the question of how much does solar output change during a solar cycle still comes with a ~20% measurement uncertainty.
Honestly, Section 4 is mostly there to provide a path of succession when the President is physically unable to serve but is not dead (e.g. comatose or otherwise medically incapacitated).
January 20, 2026 at 1:44 PM
Honestly, Section 4 is mostly there to provide a path of succession when the President is physically unable to serve but is not dead (e.g. comatose or otherwise medically incapacitated).
Reposted by Robert Rohde
We're one year in. The speed, scope and severity of what's happening to American science is beyond anything we've seen before. The reliability of the Federal science and technology enterprise and the people within it, has been shattered. www.nature.com/articles/d41...
‘Shattered’: US scientists speak out about how Trump policies disrupted their careers
Researchers lay bare the human toll of lay-offs, funding cuts and attacks on science one year after the president’s return to the White House.
www.nature.com
January 20, 2026 at 12:42 PM
We're one year in. The speed, scope and severity of what's happening to American science is beyond anything we've seen before. The reliability of the Federal science and technology enterprise and the people within it, has been shattered. www.nature.com/articles/d41...
Presumably they didn't export either. I'll check later.
January 20, 2026 at 10:05 AM
Presumably they didn't export either. I'll check later.
Something's apparently wrong with our automated export process.
I'm going to update the tables manually later today.
I'm going to update the tables manually later today.
January 20, 2026 at 10:00 AM
Something's apparently wrong with our automated export process.
I'm going to update the tables manually later today.
I'm going to update the tables manually later today.
For further discussion, see yesterday's thread and
@berkeleyearth.org's Annual Report.
bsky.app/profile/did:...
@berkeleyearth.org's Annual Report.
bsky.app/profile/did:...
While the world sometimes seems metaphorically on fire right now, global warming is still progressing as well.
In 2025, global warming delivered the 3rd warmest year since measurements began. A modest step down from 2024's records, but still well above 20th century norms.
🧪🧵
In 2025, global warming delivered the 3rd warmest year since measurements began. A modest step down from 2024's records, but still well above 20th century norms.
🧪🧵
January 20, 2026 at 9:50 AM
For further discussion, see yesterday's thread and
@berkeleyearth.org's Annual Report.
bsky.app/profile/did:...
@berkeleyearth.org's Annual Report.
bsky.app/profile/did:...
Nearly linear warming over recent decades is in line with what models expect based on the observed history of greenhouse gases that have been added to the atmosphere.
But the warming experienced in 2023, 2024, and 2025 suggest additional factor(s) are having an effect.
But the warming experienced in 2023, 2024, and 2025 suggest additional factor(s) are having an effect.
January 20, 2026 at 9:50 AM
Nearly linear warming over recent decades is in line with what models expect based on the observed history of greenhouse gases that have been added to the atmosphere.
But the warming experienced in 2023, 2024, and 2025 suggest additional factor(s) are having an effect.
But the warming experienced in 2023, 2024, and 2025 suggest additional factor(s) are having an effect.
For 50 years, global warming had a very consistent trend (+0.19 °C/decade) with a boring, predictable range of natural variations around it.
During the last three years, we've broken out above that range, suggesting the pace of change has quickened.
During the last three years, we've broken out above that range, suggesting the pace of change has quickened.
January 20, 2026 at 9:50 AM
For 50 years, global warming had a very consistent trend (+0.19 °C/decade) with a boring, predictable range of natural variations around it.
During the last three years, we've broken out above that range, suggesting the pace of change has quickened.
During the last three years, we've broken out above that range, suggesting the pace of change has quickened.
For more background on 2025 temperatures from a climate context, please see @berkeleyearth.org's annual report:
berkeleyearth.org/global-tempe...
berkeleyearth.org/global-tempe...
Global Temperature Report for 2025 - Berkeley Earth
2025 was the 3rd warmest year on Earth since direct observations began, and recent warming appears to be moving faster than expected.
berkeleyearth.org
January 20, 2026 at 12:15 AM
For more background on 2025 temperatures from a climate context, please see @berkeleyearth.org's annual report:
berkeleyearth.org/global-tempe...
berkeleyearth.org/global-tempe...
2026 seems likely to deliver more of the same.
Warmth well above 20th century averages, and probably similar to 2025, but only a modest (10%) chance of a new record.
A switch to El Niño later this year is possible, but if so, would probably impact 2027 more than 2026.
Warmth well above 20th century averages, and probably similar to 2025, but only a modest (10%) chance of a new record.
A switch to El Niño later this year is possible, but if so, would probably impact 2027 more than 2026.
January 20, 2026 at 12:14 AM
2026 seems likely to deliver more of the same.
Warmth well above 20th century averages, and probably similar to 2025, but only a modest (10%) chance of a new record.
A switch to El Niño later this year is possible, but if so, would probably impact 2027 more than 2026.
Warmth well above 20th century averages, and probably similar to 2025, but only a modest (10%) chance of a new record.
A switch to El Niño later this year is possible, but if so, would probably impact 2027 more than 2026.
So, in 2025, we had:
Warming from increased greenhouse gases
Warming from reduced marine sulfur
Cooling from La Niña
Warming from an active solar cycle
Warming(?) from Hunga Tonga
And arrive at the third warmest year in the modern record.
Warming from increased greenhouse gases
Warming from reduced marine sulfur
Cooling from La Niña
Warming from an active solar cycle
Warming(?) from Hunga Tonga
And arrive at the third warmest year in the modern record.
January 20, 2026 at 12:13 AM
So, in 2025, we had:
Warming from increased greenhouse gases
Warming from reduced marine sulfur
Cooling from La Niña
Warming from an active solar cycle
Warming(?) from Hunga Tonga
And arrive at the third warmest year in the modern record.
Warming from increased greenhouse gases
Warming from reduced marine sulfur
Cooling from La Niña
Warming from an active solar cycle
Warming(?) from Hunga Tonga
And arrive at the third warmest year in the modern record.
A recent modeling attempting to simulate the full impact of the volcano suggests that the eruption might have initially created modest cooling only to be followed by modest warming after the sulfur aerosols had dissipated.
juser.fz-juelich.de/record/10491...
Reality can be messy.
juser.fz-juelich.de/record/10491...
Reality can be messy.
juser.fz-juelich.de
January 20, 2026 at 12:11 AM
A recent modeling attempting to simulate the full impact of the volcano suggests that the eruption might have initially created modest cooling only to be followed by modest warming after the sulfur aerosols had dissipated.
juser.fz-juelich.de/record/10491...
Reality can be messy.
juser.fz-juelich.de/record/10491...
Reality can be messy.
Water vapor is a strong greenhouse gas, and so its excess (especially in the normally dry upper atmosphere) could lead to warming.
At the same time Hunga Tonga unleashed sulfur aerosols that would be expected to lead to cooling.
The net effect is... complicated.
At the same time Hunga Tonga unleashed sulfur aerosols that would be expected to lead to cooling.
The net effect is... complicated.
January 20, 2026 at 12:11 AM
Water vapor is a strong greenhouse gas, and so its excess (especially in the normally dry upper atmosphere) could lead to warming.
At the same time Hunga Tonga unleashed sulfur aerosols that would be expected to lead to cooling.
The net effect is... complicated.
At the same time Hunga Tonga unleashed sulfur aerosols that would be expected to lead to cooling.
The net effect is... complicated.
Unlike the lower atmosphere, where water vapor typically persists for only 1-2 weeks before raining out, the upper atmosphere takes years to dissipate any excess water vapor.
Hunga Tonga provided an unprecedented natural experiment for upper atmosphere water vapor.
Hunga Tonga provided an unprecedented natural experiment for upper atmosphere water vapor.
January 20, 2026 at 12:11 AM
Unlike the lower atmosphere, where water vapor typically persists for only 1-2 weeks before raining out, the upper atmosphere takes years to dissipate any excess water vapor.
Hunga Tonga provided an unprecedented natural experiment for upper atmosphere water vapor.
Hunga Tonga provided an unprecedented natural experiment for upper atmosphere water vapor.
In addition to the reduction of marine sulfur air pollution, the other X factor in recent years is the January 2022 eruption of the Hunga Tonga volcano.
An eruption that provided a never before seen boost in upper atmosphere water vapor content.
x.com/RARohde/stat...
An eruption that provided a never before seen boost in upper atmosphere water vapor content.
x.com/RARohde/stat...
x.com
January 20, 2026 at 12:09 AM
In addition to the reduction of marine sulfur air pollution, the other X factor in recent years is the January 2022 eruption of the Hunga Tonga volcano.
An eruption that provided a never before seen boost in upper atmosphere water vapor content.
x.com/RARohde/stat...
An eruption that provided a never before seen boost in upper atmosphere water vapor content.
x.com/RARohde/stat...
In 2025, we actually started and ended the year with a mild La Niña event. This contrasts with the El Niño of 2023/2024.
But for the cooling provided by La Niña, 2025 likely would have been warmer.
But even with a La Niña, 2025 was above the long-term trend line.
But for the cooling provided by La Niña, 2025 likely would have been warmer.
But even with a La Niña, 2025 was above the long-term trend line.
January 20, 2026 at 12:09 AM
In 2025, we actually started and ended the year with a mild La Niña event. This contrasts with the El Niño of 2023/2024.
But for the cooling provided by La Niña, 2025 likely would have been warmer.
But even with a La Niña, 2025 was above the long-term trend line.
But for the cooling provided by La Niña, 2025 likely would have been warmer.
But even with a La Niña, 2025 was above the long-term trend line.
Ultimately, removing sulfur air pollution simply reveals the warming that Earth would have had anyway from added greenhouse gases, if we hadn't also been polluting the air with sulfur.
However, removing that sulfur does still provide a bit a shock/jump.
However, removing that sulfur does still provide a bit a shock/jump.
January 20, 2026 at 12:08 AM
Ultimately, removing sulfur air pollution simply reveals the warming that Earth would have had anyway from added greenhouse gases, if we hadn't also been polluting the air with sulfur.
However, removing that sulfur does still provide a bit a shock/jump.
However, removing that sulfur does still provide a bit a shock/jump.
Natural variability still plays a role, but the reduction in marine sulfur air pollution (and associated reduction in low cloud cover) likely contributed to the North Pacific heatwave we saw last year, and the North Atlantic heatwaves of 2023/2024.
January 20, 2026 at 12:08 AM
Natural variability still plays a role, but the reduction in marine sulfur air pollution (and associated reduction in low cloud cover) likely contributed to the North Pacific heatwave we saw last year, and the North Atlantic heatwaves of 2023/2024.
Sulfur air pollution reflects sunlight and creates condensation nuclei that encourage cloud formation.
This provides a measure of cooling.
By abruptly reducing the marine sulfur air pollution, especially in the North Atlantic & North Pacific, these regions get a warming boost.
This provides a measure of cooling.
By abruptly reducing the marine sulfur air pollution, especially in the North Atlantic & North Pacific, these regions get a warming boost.
January 20, 2026 at 12:07 AM
Sulfur air pollution reflects sunlight and creates condensation nuclei that encourage cloud formation.
This provides a measure of cooling.
By abruptly reducing the marine sulfur air pollution, especially in the North Atlantic & North Pacific, these regions get a warming boost.
This provides a measure of cooling.
By abruptly reducing the marine sulfur air pollution, especially in the North Atlantic & North Pacific, these regions get a warming boost.