"[NASEM] found that the evidence linking rising greenhouse gas emissions to negative human health outcomes is 'beyond scientific dispute.'”
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I've often found myself listing the major negatives of the fossil fuel industries (lung damage, ecological damage, the warping of international relations, the spurring of resource wars, noisy combustion vehicles crowding cities, etc.) without even getting to the bit about greenhouse gases, climate change or SLR.
Evidence linking combustion products to negative human health outcomes is "beyond scientific dispute."
"(although China, with a population 4x bigger than the U.S., has been a bigger annual contributor for the last two decades)"
----
My usual note: China has become a manufacturing center for much of world, so some of the carbon footprint used to make, say, my carts and steel shelves, are on me, here in the US.
Just a slight comment on a statement in the second paragraph. It is the atmospheric perturbation of the CO2 concentration that has a long lifetime. The lifetime of a particular CO2 molecule in the atmosphere is only 4-5 years or so, being taken up by the active terrestrial biosphere or upper wind-mixed layer of the ocean. There are many examples of confusion about this and I personally think we ought to be a bit more precise in making this clear.
Yes, you're correct. Nevertheless, the essential point he's making is correct. If we increase CO2 in the atmosphere, it will be a long time before CO2 has returned to the pre-perturbation value.
I agree, although there are leading scientists who have said something differently. As near as I can tell, the issue is if the net carbon flux from the mixed layer to the deep ocean will continue as at present as it is driven by the gradient between the mixed layer and deep ocean and that does not change much if emissions go to zero. If this occurs, then the atmosphere-mixed layer would stay roughly at it is and so the flux from atmosphere to mixed layer would continue and so the lifetime of the atmospheric perturbation will be shorter. Then there has been mistaken interpretation of what will happen at net zero suggesting one that is reached the atmospheric concentration will drop by half--but this was a confusion with the already accounted for atmospheric fraction being of order 0.5. Then there is the issue that the radiative forcing gradient is due to multiple GHGs and each has its own lifetimes, so what happens will not be dependent just on CO2 (e.g., tropospheric ozone, black carbon, methane all have short lifetimes). An interesting question is what happens for the full set of gases headed down toward zero. Focusing on just CO2 is thus too simple to be realistic.
Depends on what you call realistic. The consensus estimate of *fossil* CO2's contribution to the rate of total warming is around 75-80%, combining with other anthropogenic factors to account for 110% (https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans/). The over-attribution is because of the historical cooling effects of anthropogenic aerosols, now dissipating in the stratosphere.
Bearing in mind all known causes of the rising trend of global heat content, eliminating the transfer of fossil carbon to the atmosphere by the gigatonnes annually should reduce the slope of the trend substantially, hopefully buying time to alleviate the other anthropogenic causes.
“Inland flood histories are too statistically noisy to be used as a metric of climate change.” But it “has atmospheric warming written all over it.” What?
There is a theory that says it should happen, but no evidence that it did happen. Yet, regarding the Hill Country floods, Dessler states, without qualification, that climate change acts like “steroids for the weather”. Based on what? A hope and a prayeR.
As a result of an extreme →rain event← (you know, the *weather*), there was a massive flood in the Hill Country. Erratic flood history and death rates* that the doubt-mongers obsess on and use to distract are not the issue. The tie to climate change is the *weather*.
Flooding is not weather. People camping in desert arroyos can be killed by flooding from rainfall miles away. Flooding can come from dam breaks. Flooding can come from rising tides. Flooding can come from broken water mains. Flooding can come from blocked or re-directed water flows.
And the metaphor that "climate change acts like steroids for the weather" is an old one. The fact that you don't recognize that and treat the phrase as if Dessler just made it up tells me you haven't been following climate science research in any depth.
global warming → more heat in the atmosphere
more heat in the atmosphere → more extreme weather
more extreme weather → "weather on steroids"
____________________
*Note that the death rate was increased by a factor not related to the weather: The very heavy rainfall occurred on the Fourth of July weekend, when a lot of people came in to the area to camp along rivers.
Good description of a theory of the potential influence of CC on rainfall intensity during storms. But what are the quantitative magnitudes of the CC-related components relative to the numerous other in-situ factors also influencing rainfall intensity? Historical data from the Texas Hill Country flash floods indicates that if CC affected the rainfall intensity, its magnitude was too small to be evident above the noise. The DOE report also indicates the CC-related components are insufficient to appreciably impact storm frequency or intensity.
Inland flood histories are too statistically noisy to be used as a metric of climate change.
Because flooding is a result of so many parameters (vegetation status, pre-existing soil saturation, burn scar and impervious cover, snow and ice melt, the placement of storms across multiple watersheds, etc.), we shouldn't be looking at the history of Hill Country flash floods, but of the history of Hill Country →rain events←.
The rain event that caused the deadly Fourth of July floods added over 490,000,000 cubic meters of water to Lake Travis. (I believe the technical term for this is "a mighty fuckton of water.") That has atmospheric warming written all over it.
“Inland flood histories are too statistically noisy to be used as a metric of climate change.” But it “has atmospheric warming written all over it.” What?
There is a theory that says it should happen, but no evidence that it did happen. Yet, regarding the Hill Country floods, Dessler states, without qualification, that climate change acts like “steroids for the weather”. Based on what? A hope and a praye
As a result of an extreme →rain event← (you know, the *weather*), there was a massive flood in the Hill Country. Erratic flood history and death rates* that the doubt-mongers obsess on and use to distract are not the issue. The tie to climate change is the *weather*.
Flooding is not weather. People camping in desert arroyos can be killed by flooding from rainfall miles away. Flooding can come from dam breaks. Flooding can come from rising tides. Flooding can come from broken water mains. Flooding can come from blocked or re-directed water flows.
And the metaphor that "climate change acts like steroids for the weather" is an old one. The fact that you don't recognize that and treat the phrase as if Dessler just made it up tells me you haven't been following climate science research in any depth.
global warming → more heat in the atmosphere
more heat in the atmosphere → more extreme weather
more extreme weather → "weather on steroids"
____________________
*Note that the death rate was increased by a factor not related to the weather: The very heavy rainfall occurred on the Fourth of July weekend, when a lot of people came in to the area to camp along rivers.
"Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has strengthened since AR5."
The report goes into excruciating detail about all the ways your comment is wrong!
If only we could rely on summaries for policy makers. It's those pesky details that get in the way. So, I actually clicked on your link and decided to check out the references for "observed trends". Guess what the first paragraph says?
I quote directly: "The SREX (Seneviratne et al., 2012) assessed low confidence for observed changes in the magnitude or frequency of floods at the global scale. This assessment was confirmed by AR5 (Hartmann et al., 2013). The SR1.5 (Hoegh-Guldberg et al., 2018) found increases in flood frequency and extreme streamflow in some regions, but decreases in other regions. While the number of studies on flood trends has increased since AR5, and there were also new analyses after the release of SR1.5 (Berghuijs et al., 2017; Blöschl et al., 2019; Gudmundsson et al., 2019), hydrological literature on observed flood changes is heterogeneous, focusing at regional and sub-regional basin scales, making it difficult to synthesize at the global and sometimes regional scales."
In other words, Mal, the very first paragraph says that they don't even know if floods are increasing or decreasing globally. Now, you tell me--how do we get to "Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones and in particular their attribution to human influence has strengthended since AR5"? It almost seems like the summary for policy makers and the actual report are authored by 2 very different groups of people. Do uou know holw to look at studies?
At this time "the continents now contribute more freshwater to sea level rise than the ice sheets, and drying regions now contribute more than land glaciers and ice caps" (and thermal expansion hasn't really kicked in yet).
Thank you for your presentation. How do you reconcile your findings with the findings of Alimonti, et. al. regarding actual observed global natural disaster trends showing that "most recent subperiod 2002–2022 characterized by a significant decline in number of events"?
Is SLR that threatens coast residents (including taking out land that people of Bangladesh have lived on for generations, pushing them into the slums of Dhaka) considered a "disaster" as they define it?
Is drought, even *flash drought*, considered a "disaster" as they define it?
Are sustained record crown wildfires considered a single "disaster" independent of how much material is burned?
That is why I provided a link for you above. Natural disaster frequency has not increased in EMDAT database since 2000, which is the year that we can start comparing apples to apples. All years before that EMDAT states are biased low due to availability bias.
If you have any studies to the contrary, please provide them. It may be difficult because EMDAT seems to be the gold standard, as deficient as it is. They don't "model" the future, they record events globally as they happen.
If climate change is worsening, then this would play out in the real world, observable data--not climate models.
NS--perhaps you should start your own database and record changes over time. Anecdotal data doesn't really prove anything. If SLR events are increasing globally, your database will show it. If mass of forest burned area is increasing, your database will show it (spoiler alert: We already know the trends are down globally on this one, sorry). If flash droughts are increasing globally, your database will show it. Otherwise, it's seems to me just more anecdotes. Those don't fly in "science methodology airlines". Read the details of IPCC report. The summary for policy makers and the actual science are two very different things.
Why are you labeling these examples as "anecdotes"? They're relevant to how that paper† specifies what it calls a disaster, or even why the →count← of "events" matters when they vary so greatly in cost or damage.
The point is to find out how it/you define what counts as a disaster, and whether that particular metric is relevant to the problems of accelerating global warming. Does the paper state what this data is supposed to be a proxy for?
I note that you don't discuss the *measure* of increasing melt of land ice and its direct causal connection to accelerating global mean SLR, or the *measure* of the increasing loss of large swaths of coral reefs to higher sea temperatures, or the *measure* of the shift of the US' Tornado Alley, or the *measures* of the slowing of various critical segments of the AMOC?
____________
†I can't access that paper so I asked that you provide certain information on what was in it.
EMDAT database: storms (cyclones, tornadoes, hail, etc), floods, tsunamis, etc. extreme temperature events, landslides, earthquakes, volcano eruptions, droughts, wildfires, epidemics (virus, bacterial, etc), space weather events, etc.
All no trend when corrected for availability and reporting biases.
If you want to include sea level rise as a natural disaster, then you'll need to show how the 4.4 inches increase over the past 30 years has created a recordable natural disaster.
Dear Kevin, thank you for this analysis. I was intrigued by your discussion of humidity, given that recent CERES data shows that subtropical cloud cover is rapidly decreasing. This seems to imply that warming causes the additional water in the atmosphere to shift more from liquid to vapor. Is that correct? In that context, how can the additional humidity cause the extra rain you describe, given that rain only comes from liquid clouds? A second point, I was disappointed by your claim that the only alternatives are decarbonisation and adaptation. It is essential to recognise sunlight reflection technologies as a major emerging climate factor.
CERES data show a lot of ups and downs, and the trend recently has been back closer to the average. The main decrease in cloud is in the subtropics and is caused by a poleward shift in the jet stream and storm tracks. A detailed analysis is in this paper:Trenberth. K.E., L. Cheng, Y. Pan, J. Fasullo and M. Mayer, 2025: Distinctive pattern of global warming in ocean heat content J. Climate, 38, 2155-2168 https://doi.org/10.1175/JCLI-D-24-0609.1
The doi link here is open access. The figures show a lot more on all aspects of what is going on involving atmospheric and ocean circulation.
CERES data I have seen shows albedo hovering with slight decline from 99.8 watts per square meter (w) in 2000 to 99.4w in 2013, then a collapse by 2w to 97.4w in 2023, rebounding by 0.6w in 2024 to 98w. 2013-23 is a decadal fall of two watts per square meter in Earth albedo reflectivity. In this dataset, shared by Peter Cox of Exeter University, the last year, 2024, returned toward the mean, but the trend is down. Chart is at Peter Cox's Climate Chat interview with Dan Miller at https://youtu.be/5rsIoJeveOM?t=1057
This 2w increase in radiative forcing from the darkening of the planet over the decade to 2023 appears to be five times the ~0.4w RF from emissions in that decade.
My understanding, from Hansen et al Global Warming in the Pipeline and subsequent, is that the primary factor in this albedo collapse is the vanishing of subtropical marine clouds. They calculate cloud loss at ~50% of albedo loss.
The main explanation I have heard of this is that the protective inversion layer of air sitting on top of these clouds is disrupted by warming. The clouds mix with the inversion layer, causing evaporation and reducing cloud formation, generating an accelerating warming feedback as more light hits the ocean.
I hope this is correct and would welcome comment. Also it would be of great interest Kevin if you could comment on the balance between jet stream disruption and inversion layer disintegration as factors in cloud loss. I have not yet read your whole paper, thank you for sharing it.
Hansen is quite wrong as he blames it all on shipborne aerosols. But the biggest warming is in the southern hemisphere where that is not a factor! You need to read our article.
Heat over certain areas of land can cause high pressure domes of dry air (which I feel here on land as being in a roaster), and clear, cloudless skies. Heat over water bodies (or swampy ground) pulls water up and out. This water supply can be pulled over [other] land and be dumped there, sometimes in high quantities in short amounts of time. This includes simple thunderstorms, cyclone "feeder bands" bearing rain clouds, and—biggest of all, and definitely familiar to US and European west coasters—atmospheric rivers that can pump a long train of rain clouds over land.
Also compare the "lake effect" precipitation from a westerly wind that can pull water content out of a warm Lake Erie and dump it almost immediately on Buffalo and surrounding areas in the form of heavy snow (or rain). The amount of precipitation is very heavy and focused, even if the cloud cover itself isn't broad.
[OK, this is a crude simplification in the presence of weather experts, but it more than handles how a reduction in cloud cover over continents can at the same time include increased spikes of rainfall events.]
"But it is more than the overall rise in temperatures that is in play. Changes also relate to location, especially land versus ocean, and weather and weather patterns."
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There are also the idiosyncrasies of various species of flora and fauna that have unknown vulnerabilities. A small increase in winter warmth in North America, for instance, tipped the balance in terms of what percentage of pine bark beetles survived over the winter (with a boost from natural selection, no doubt). Trees that reproduce over decades can be wiped out by insects that reproduce multiple times a year. That's where the forest's opportunistic tree/plant species fill in, though they, too, can be taken out by too-warm winters (or too-warm nighttime temps).
This is why we have to drop the idea of restoring previous native species and focus on what can survive and thrive and construct its own new habitat, and crank up the GMO adaptations for both cultivated and wild plants.
I think it is more important to work towards reversing global warming; trying to adjust is like trying to adapt to a moving target. WE MUST FOCUS ON SOLUTIONS.
The main causes of climate destabilization and global warming induced vicious cycles are the high greenhouse gas levels - they are partly high due to the loss of vegetation - about `1/5 since 1850, largely due to beef production, today utilizing 75-80% of all arable land. If beef production would be decimated and much of this land would be reforested, returned to a natural state of high prairies and wet lands, most excess CO2 would be removed from the atmosphere. In addition, we can plant bamboo, other rapidly growing plants like algae; and there are some 9 million km2 of land that is not used by humans, which could be reforested with over a trillion trees. (The lush vegetation would immediately improve the local climate.) For long-term sequestration of carbon, we also can prevent much of the decomposing of dead plant material and other organic matters, keeping it dry and/or cold (in heaps protected with roofs), by sinking wood into deep lakes or cold oceans, immersing organic material in stagnant water, covered with plants (such as duck weed in warm, peat moss in cool areas). Just burying dead wood, covered with clay, greatly slows decomposition.
However, we need comprehensive emergency government actions, which will not happen unless NGOs, activists and informed people demand it. Not working towards these goals is cruel, maybe genocidal - the poor cannot adapt to the rapidly worsening weather catastrophes.
Please help us educate the people regarding solutions - grassroots movements must coalesce to form a mass movement that demands a radical, effective government response - we must lead, other countries will almost certainly follow.
Should we not emphasize the need for adaptation to the effects of CO2 accumulation that has already occurred. not just to the accumulation in the future that will be affected by policy?
Yes, we 100% need to adapt to climate change that has already occurred and that which we cannot avoid. And we should work hard to avoid the climate change that we is avoidable.
Adaptation to the effects of CO2 accumulation that has already occurred is being done locally and privately. Insurance providers, for example, are adapting by raising rates or abandoning vulnerable areas. National assistance, e.g. FEMA, can assist local efforts, but adaptation will happen one way or another, one home or community at a time, even without emphasizing the need to those who haven't yet been impacted by climate change. The victims of newly extreme weather know what adaptation means to them (https://www.pressreader.com/usa/austin-american-statesman/20250829/281638196319748)!
Mitigation, OTOH, i.e. curtailing the transfer of fossil carbon to the atmosphere by the gigatonnes annually, requires collective intervention in the otherwise-"free" market for energy. In the USA, that means a majority must vote for Democratic candidates in every election, at least until some Republican candidate defies their party's dogged denialism and publicly supports collective intervention to take the profit out of selling fossil fuel. For better or worse, the Democrats are currently the party of collective action for public good in this country. How hard can that be to acknowledge?
The difference between collective v non-collective response is a good point. Insurance is allowed to use forward-looking risk assessing models for rate setting will be an important driver of adaptation. And given federal involvement in other infrastructure, climate adaption infrastructure may be no different.
Isn't "federal involvement" withdrawing on all points? FEMA is gutted, contracts are being pulled, personal extortionate conditions are being added to both existing and new grant allocations.
Thanks for that link to The Electric Slide!
China is the Secretariat leading the pack by 31 lengths.
"[NASEM] found that the evidence linking rising greenhouse gas emissions to negative human health outcomes is 'beyond scientific dispute.'”
----
I've often found myself listing the major negatives of the fossil fuel industries (lung damage, ecological damage, the warping of international relations, the spurring of resource wars, noisy combustion vehicles crowding cities, etc.) without even getting to the bit about greenhouse gases, climate change or SLR.
Evidence linking combustion products to negative human health outcomes is "beyond scientific dispute."
"(although China, with a population 4x bigger than the U.S., has been a bigger annual contributor for the last two decades)"
----
My usual note: China has become a manufacturing center for much of world, so some of the carbon footprint used to make, say, my carts and steel shelves, are on me, here in the US.
Just a slight comment on a statement in the second paragraph. It is the atmospheric perturbation of the CO2 concentration that has a long lifetime. The lifetime of a particular CO2 molecule in the atmosphere is only 4-5 years or so, being taken up by the active terrestrial biosphere or upper wind-mixed layer of the ocean. There are many examples of confusion about this and I personally think we ought to be a bit more precise in making this clear.
Yes, you're correct. Nevertheless, the essential point he's making is correct. If we increase CO2 in the atmosphere, it will be a long time before CO2 has returned to the pre-perturbation value.
I agree, although there are leading scientists who have said something differently. As near as I can tell, the issue is if the net carbon flux from the mixed layer to the deep ocean will continue as at present as it is driven by the gradient between the mixed layer and deep ocean and that does not change much if emissions go to zero. If this occurs, then the atmosphere-mixed layer would stay roughly at it is and so the flux from atmosphere to mixed layer would continue and so the lifetime of the atmospheric perturbation will be shorter. Then there has been mistaken interpretation of what will happen at net zero suggesting one that is reached the atmospheric concentration will drop by half--but this was a confusion with the already accounted for atmospheric fraction being of order 0.5. Then there is the issue that the radiative forcing gradient is due to multiple GHGs and each has its own lifetimes, so what happens will not be dependent just on CO2 (e.g., tropospheric ozone, black carbon, methane all have short lifetimes). An interesting question is what happens for the full set of gases headed down toward zero. Focusing on just CO2 is thus too simple to be realistic.
Depends on what you call realistic. The consensus estimate of *fossil* CO2's contribution to the rate of total warming is around 75-80%, combining with other anthropogenic factors to account for 110% (https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans/). The over-attribution is because of the historical cooling effects of anthropogenic aerosols, now dissipating in the stratosphere.
Bearing in mind all known causes of the rising trend of global heat content, eliminating the transfer of fossil carbon to the atmosphere by the gigatonnes annually should reduce the slope of the trend substantially, hopefully buying time to alleviate the other anthropogenic causes.
This is the best carbon cycle animation ever: Watch the flow of the red dots.
(You might find this more watchable at a different speed.)
https://www.youtube.com/watch?v=dwVsD9CiokY
“Inland flood histories are too statistically noisy to be used as a metric of climate change.” But it “has atmospheric warming written all over it.” What?
There is a theory that says it should happen, but no evidence that it did happen. Yet, regarding the Hill Country floods, Dessler states, without qualification, that climate change acts like “steroids for the weather”. Based on what? A hope and a prayeR.
As a result of an extreme →rain event← (you know, the *weather*), there was a massive flood in the Hill Country. Erratic flood history and death rates* that the doubt-mongers obsess on and use to distract are not the issue. The tie to climate change is the *weather*.
Flooding is not weather. People camping in desert arroyos can be killed by flooding from rainfall miles away. Flooding can come from dam breaks. Flooding can come from rising tides. Flooding can come from broken water mains. Flooding can come from blocked or re-directed water flows.
And the metaphor that "climate change acts like steroids for the weather" is an old one. The fact that you don't recognize that and treat the phrase as if Dessler just made it up tells me you haven't been following climate science research in any depth.
global warming → more heat in the atmosphere
more heat in the atmosphere → more extreme weather
more extreme weather → "weather on steroids"
____________________
*Note that the death rate was increased by a factor not related to the weather: The very heavy rainfall occurred on the Fourth of July weekend, when a lot of people came in to the area to camp along rivers.
Good description of a theory of the potential influence of CC on rainfall intensity during storms. But what are the quantitative magnitudes of the CC-related components relative to the numerous other in-situ factors also influencing rainfall intensity? Historical data from the Texas Hill Country flash floods indicates that if CC affected the rainfall intensity, its magnitude was too small to be evident above the noise. The DOE report also indicates the CC-related components are insufficient to appreciably impact storm frequency or intensity.
Inland flood histories are too statistically noisy to be used as a metric of climate change.
Because flooding is a result of so many parameters (vegetation status, pre-existing soil saturation, burn scar and impervious cover, snow and ice melt, the placement of storms across multiple watersheds, etc.), we shouldn't be looking at the history of Hill Country flash floods, but of the history of Hill Country →rain events←.
The rain event that caused the deadly Fourth of July floods added over 490,000,000 cubic meters of water to Lake Travis. (I believe the technical term for this is "a mighty fuckton of water.") That has atmospheric warming written all over it.
“Inland flood histories are too statistically noisy to be used as a metric of climate change.” But it “has atmospheric warming written all over it.” What?
There is a theory that says it should happen, but no evidence that it did happen. Yet, regarding the Hill Country floods, Dessler states, without qualification, that climate change acts like “steroids for the weather”. Based on what? A hope and a praye
As a result of an extreme →rain event← (you know, the *weather*), there was a massive flood in the Hill Country. Erratic flood history and death rates* that the doubt-mongers obsess on and use to distract are not the issue. The tie to climate change is the *weather*.
Flooding is not weather. People camping in desert arroyos can be killed by flooding from rainfall miles away. Flooding can come from dam breaks. Flooding can come from rising tides. Flooding can come from broken water mains. Flooding can come from blocked or re-directed water flows.
And the metaphor that "climate change acts like steroids for the weather" is an old one. The fact that you don't recognize that and treat the phrase as if Dessler just made it up tells me you haven't been following climate science research in any depth.
global warming → more heat in the atmosphere
more heat in the atmosphere → more extreme weather
more extreme weather → "weather on steroids"
____________________
*Note that the death rate was increased by a factor not related to the weather: The very heavy rainfall occurred on the Fourth of July weekend, when a lot of people came in to the area to camp along rivers.
Even the IPCC says there is no evidence for increase in extreme weather..
False. From the AR6 WG1 Summary for Policy Makers (https://www.ipcc.ch/report/ar6/wg1/chapter/summary-for-policymakers):
"Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has strengthened since AR5."
The report goes into excruciating detail about all the ways your comment is wrong!
Mal,
If only we could rely on summaries for policy makers. It's those pesky details that get in the way. So, I actually clicked on your link and decided to check out the references for "observed trends". Guess what the first paragraph says?
I quote directly: "The SREX (Seneviratne et al., 2012) assessed low confidence for observed changes in the magnitude or frequency of floods at the global scale. This assessment was confirmed by AR5 (Hartmann et al., 2013). The SR1.5 (Hoegh-Guldberg et al., 2018) found increases in flood frequency and extreme streamflow in some regions, but decreases in other regions. While the number of studies on flood trends has increased since AR5, and there were also new analyses after the release of SR1.5 (Berghuijs et al., 2017; Blöschl et al., 2019; Gudmundsson et al., 2019), hydrological literature on observed flood changes is heterogeneous, focusing at regional and sub-regional basin scales, making it difficult to synthesize at the global and sometimes regional scales."
In other words, Mal, the very first paragraph says that they don't even know if floods are increasing or decreasing globally. Now, you tell me--how do we get to "Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones and in particular their attribution to human influence has strengthended since AR5"? It almost seems like the summary for policy makers and the actual report are authored by 2 very different groups of people. Do uou know holw to look at studies?
More horse shit on climate change...
You have an opportunity to make some money by investing as if climate change is a hoax!
GRACE satellite data shows accelerating loss of continental water stores:
https://thinc.blog/2025/09/21/pbs-on-our-drying-planet/
At this time "the continents now contribute more freshwater to sea level rise than the ice sheets, and drying regions now contribute more than land glaciers and ice caps" (and thermal expansion hasn't really kicked in yet).
Les cris d'alarme et les analyses doivent être suivis par les actions.
Kevin,
Thank you for your presentation. How do you reconcile your findings with the findings of Alimonti, et. al. regarding actual observed global natural disaster trends showing that "most recent subperiod 2002–2022 characterized by a significant decline in number of events"?
https://www.tandfonline.com/doi/full/10.1080/17477891.2023.2239807
Their real world findings using EMDAT seem to contradict your theoretical logistics.
I don't have access to that paper.
Is SLR that threatens coast residents (including taking out land that people of Bangladesh have lived on for generations, pushing them into the slums of Dhaka) considered a "disaster" as they define it?
Is drought, even *flash drought*, considered a "disaster" as they define it?
Are sustained record crown wildfires considered a single "disaster" independent of how much material is burned?
Thanks in advance.
That is why I provided a link for you above. Natural disaster frequency has not increased in EMDAT database since 2000, which is the year that we can start comparing apples to apples. All years before that EMDAT states are biased low due to availability bias.
If you have any studies to the contrary, please provide them. It may be difficult because EMDAT seems to be the gold standard, as deficient as it is. They don't "model" the future, they record events globally as they happen.
If climate change is worsening, then this would play out in the real world, observable data--not climate models.
The link just goes to an abstract.
So they don't count events related to SLR (e.g., increased sunny day flooding) as "disasters" you mean.
They don't count the loss of generational land in Bangladesh as a "disaster".
They don't count the increasing mass of forest burned as a "disaster".
They don't count flash droughts as a "disaster".
They don't count the accelerating disappearance of land ice a "disaster".
They don't count the thawing permafrost leading to more subsurface gas blowouts as a "disaster".
Then what in the world are they good for?
NS--perhaps you should start your own database and record changes over time. Anecdotal data doesn't really prove anything. If SLR events are increasing globally, your database will show it. If mass of forest burned area is increasing, your database will show it (spoiler alert: We already know the trends are down globally on this one, sorry). If flash droughts are increasing globally, your database will show it. Otherwise, it's seems to me just more anecdotes. Those don't fly in "science methodology airlines". Read the details of IPCC report. The summary for policy makers and the actual science are two very different things.
Why are you labeling these examples as "anecdotes"? They're relevant to how that paper† specifies what it calls a disaster, or even why the →count← of "events" matters when they vary so greatly in cost or damage.
The point is to find out how it/you define what counts as a disaster, and whether that particular metric is relevant to the problems of accelerating global warming. Does the paper state what this data is supposed to be a proxy for?
I note that you don't discuss the *measure* of increasing melt of land ice and its direct causal connection to accelerating global mean SLR, or the *measure* of the increasing loss of large swaths of coral reefs to higher sea temperatures, or the *measure* of the shift of the US' Tornado Alley, or the *measures* of the slowing of various critical segments of the AMOC?
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†I can't access that paper so I asked that you provide certain information on what was in it.
EMDAT database: storms (cyclones, tornadoes, hail, etc), floods, tsunamis, etc. extreme temperature events, landslides, earthquakes, volcano eruptions, droughts, wildfires, epidemics (virus, bacterial, etc), space weather events, etc.
All no trend when corrected for availability and reporting biases.
If you want to include sea level rise as a natural disaster, then you'll need to show how the 4.4 inches increase over the past 30 years has created a recordable natural disaster.
Dear Kevin, thank you for this analysis. I was intrigued by your discussion of humidity, given that recent CERES data shows that subtropical cloud cover is rapidly decreasing. This seems to imply that warming causes the additional water in the atmosphere to shift more from liquid to vapor. Is that correct? In that context, how can the additional humidity cause the extra rain you describe, given that rain only comes from liquid clouds? A second point, I was disappointed by your claim that the only alternatives are decarbonisation and adaptation. It is essential to recognise sunlight reflection technologies as a major emerging climate factor.
CERES data show a lot of ups and downs, and the trend recently has been back closer to the average. The main decrease in cloud is in the subtropics and is caused by a poleward shift in the jet stream and storm tracks. A detailed analysis is in this paper:Trenberth. K.E., L. Cheng, Y. Pan, J. Fasullo and M. Mayer, 2025: Distinctive pattern of global warming in ocean heat content J. Climate, 38, 2155-2168 https://doi.org/10.1175/JCLI-D-24-0609.1
The doi link here is open access. The figures show a lot more on all aspects of what is going on involving atmospheric and ocean circulation.
Kevin Trenberth
Dear Kevin, thank you for this reply.
CERES data I have seen shows albedo hovering with slight decline from 99.8 watts per square meter (w) in 2000 to 99.4w in 2013, then a collapse by 2w to 97.4w in 2023, rebounding by 0.6w in 2024 to 98w. 2013-23 is a decadal fall of two watts per square meter in Earth albedo reflectivity. In this dataset, shared by Peter Cox of Exeter University, the last year, 2024, returned toward the mean, but the trend is down. Chart is at Peter Cox's Climate Chat interview with Dan Miller at https://youtu.be/5rsIoJeveOM?t=1057
This 2w increase in radiative forcing from the darkening of the planet over the decade to 2023 appears to be five times the ~0.4w RF from emissions in that decade.
My understanding, from Hansen et al Global Warming in the Pipeline and subsequent, is that the primary factor in this albedo collapse is the vanishing of subtropical marine clouds. They calculate cloud loss at ~50% of albedo loss.
The main explanation I have heard of this is that the protective inversion layer of air sitting on top of these clouds is disrupted by warming. The clouds mix with the inversion layer, causing evaporation and reducing cloud formation, generating an accelerating warming feedback as more light hits the ocean.
I hope this is correct and would welcome comment. Also it would be of great interest Kevin if you could comment on the balance between jet stream disruption and inversion layer disintegration as factors in cloud loss. I have not yet read your whole paper, thank you for sharing it.
Hansen is quite wrong as he blames it all on shipborne aerosols. But the biggest warming is in the southern hemisphere where that is not a factor! You need to read our article.
I haz lernd today.
"how can the additional humidity cause the extra rain you describe, given that rain only comes from liquid clouds? "
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Could you rephrase this, please? What are "liquid clouds"?
Higher humidity produces water vapor as gas, which can only rain when converted to liquid as cloud. But heat is causing cloud coverage to decline
Heat over certain areas of land can cause high pressure domes of dry air (which I feel here on land as being in a roaster), and clear, cloudless skies. Heat over water bodies (or swampy ground) pulls water up and out. This water supply can be pulled over [other] land and be dumped there, sometimes in high quantities in short amounts of time. This includes simple thunderstorms, cyclone "feeder bands" bearing rain clouds, and—biggest of all, and definitely familiar to US and European west coasters—atmospheric rivers that can pump a long train of rain clouds over land.
Also compare the "lake effect" precipitation from a westerly wind that can pull water content out of a warm Lake Erie and dump it almost immediately on Buffalo and surrounding areas in the form of heavy snow (or rain). The amount of precipitation is very heavy and focused, even if the cloud cover itself isn't broad.
[OK, this is a crude simplification in the presence of weather experts, but it more than handles how a reduction in cloud cover over continents can at the same time include increased spikes of rainfall events.]
"But it is more than the overall rise in temperatures that is in play. Changes also relate to location, especially land versus ocean, and weather and weather patterns."
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There are also the idiosyncrasies of various species of flora and fauna that have unknown vulnerabilities. A small increase in winter warmth in North America, for instance, tipped the balance in terms of what percentage of pine bark beetles survived over the winter (with a boost from natural selection, no doubt). Trees that reproduce over decades can be wiped out by insects that reproduce multiple times a year. That's where the forest's opportunistic tree/plant species fill in, though they, too, can be taken out by too-warm winters (or too-warm nighttime temps).
This is why we have to drop the idea of restoring previous native species and focus on what can survive and thrive and construct its own new habitat, and crank up the GMO adaptations for both cultivated and wild plants.
I think it is more important to work towards reversing global warming; trying to adjust is like trying to adapt to a moving target. WE MUST FOCUS ON SOLUTIONS.
The main causes of climate destabilization and global warming induced vicious cycles are the high greenhouse gas levels - they are partly high due to the loss of vegetation - about `1/5 since 1850, largely due to beef production, today utilizing 75-80% of all arable land. If beef production would be decimated and much of this land would be reforested, returned to a natural state of high prairies and wet lands, most excess CO2 would be removed from the atmosphere. In addition, we can plant bamboo, other rapidly growing plants like algae; and there are some 9 million km2 of land that is not used by humans, which could be reforested with over a trillion trees. (The lush vegetation would immediately improve the local climate.) For long-term sequestration of carbon, we also can prevent much of the decomposing of dead plant material and other organic matters, keeping it dry and/or cold (in heaps protected with roofs), by sinking wood into deep lakes or cold oceans, immersing organic material in stagnant water, covered with plants (such as duck weed in warm, peat moss in cool areas). Just burying dead wood, covered with clay, greatly slows decomposition.
However, we need comprehensive emergency government actions, which will not happen unless NGOs, activists and informed people demand it. Not working towards these goals is cruel, maybe genocidal - the poor cannot adapt to the rapidly worsening weather catastrophes.
Please help us educate the people regarding solutions - grassroots movements must coalesce to form a mass movement that demands a radical, effective government response - we must lead, other countries will almost certainly follow.
Heinz Aeschbach, humanecivilization.org
Should we not emphasize the need for adaptation to the effects of CO2 accumulation that has already occurred. not just to the accumulation in the future that will be affected by policy?
Yes, we 100% need to adapt to climate change that has already occurred and that which we cannot avoid. And we should work hard to avoid the climate change that we is avoidable.
Adaptation to the effects of CO2 accumulation that has already occurred is being done locally and privately. Insurance providers, for example, are adapting by raising rates or abandoning vulnerable areas. National assistance, e.g. FEMA, can assist local efforts, but adaptation will happen one way or another, one home or community at a time, even without emphasizing the need to those who haven't yet been impacted by climate change. The victims of newly extreme weather know what adaptation means to them (https://www.pressreader.com/usa/austin-american-statesman/20250829/281638196319748)!
Mitigation, OTOH, i.e. curtailing the transfer of fossil carbon to the atmosphere by the gigatonnes annually, requires collective intervention in the otherwise-"free" market for energy. In the USA, that means a majority must vote for Democratic candidates in every election, at least until some Republican candidate defies their party's dogged denialism and publicly supports collective intervention to take the profit out of selling fossil fuel. For better or worse, the Democrats are currently the party of collective action for public good in this country. How hard can that be to acknowledge?
The difference between collective v non-collective response is a good point. Insurance is allowed to use forward-looking risk assessing models for rate setting will be an important driver of adaptation. And given federal involvement in other infrastructure, climate adaption infrastructure may be no different.
Isn't "federal involvement" withdrawing on all points? FEMA is gutted, contracts are being pulled, personal extortionate conditions are being added to both existing and new grant allocations.