HN user
Cloud scientist (wet clouds, not computer clouds)
I think this is the one
https://www.energy.gov/sites/default/files/2025-07/DOE_Criti...
It is really just a collection of 'skeptic' arguments form the last 20 years or so. Science magazie had an article about it
https://www.science.org/content/article/contrarian-climate-a...
I would say we are largely past the second threshold too (that the warming is human caused). The last IPCC report had as the first statement in the summary for policymakers (from WG1 - the physical science group)
A.1 It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.
The previous report (from 2013) only said (and much further in)
Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.
The equivalent statement from AR4 (2007) was
The understanding of anthropogenic warming and cooling influences on climate has improved since the TAR, leading to very high confidence that the global average net effect of human activities since 1750 has been one of warming, ...
You could argue there is more of a question about what to do about it (e.g. try and mitigate climate change or just pay for the damanges). There is pretty good evidence at this point that mitigating the change through reducing CO2 emissions is a lot cheaper and comes with a host of other benefits (energy security, improved public health), but I can see wherer there might be arguments to have about this.
I think part of the IMO2020 compliance is that fines have actually been applied for ships that have broken previous similar regulations.
https://www.theguardian.com/world/2018/nov/26/cruise-ship-ca...
It turns out that the previous 2015 regulations around the USA and Canada were also largely followed, even offshore - this is despite there being little monitoring capability away from ports (I worked on this study).
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...
I am not an economist, but I suspect part of the compliance is a case of 'as long as everyone is forced to do it', we are okay with it as everyone can/has to raise prices.
One thing I found really interesting abou the Graphcast paper (I appreciate this is not graphcast, but I think it is still relevant) is that it doesn't understand climate change. The model requires the training data to be recent to get the best quality projections.
While there are some factors that influence predictability in the weather forecast, as the fortran code is based on physics (at least in a broad sense), it doesn't suffer from those issues in the same way.
This doesn't mean that the ML forecasts are wrong (obviously), just different. Given the relative computational simplicity of running them, I wonder if the issue is not just expertise, but also understanding how they can best be used to generate reliable weather forecasts?
I think the one time bump could be a fair description in that is doesn't add to the long term warming rate in the same way GHGs do. The cumulative effect here is pretty much all realised within about 20 years (so not an instantaneous effect, but it could be considered a one time one?)
The wording of the article and the paper are a bit misleading here. It is definitely a one time even (although it plays out over 20 years)
The doubling of the rate of warming only applies for the first year or two. Based on this paper, over the period 2020-2030, the impact of ship fuel regulations is warming of about 0.12K. The long term temperature trend is around +0.19K over this 10 year period.
The mechanism is different from the impact of sulphur in the stratosphere (where there are no clouds), but it is the same as the mechanisms that have caused the majority of the aerosol cooling (a brightening of clouds).
The same ze of the cooling has long been uncertain though. It depends a lot on assumptions you make about the pre-industrial atmosphere,something that we don't have great observations of.
The numbers in this study need to be interpreted carefully, the way the authors presented them doesn't really help this.
The warming rate they quote (0.24K per decade) is the instantaneous warming, which decreases over time. The warming over 10 years is actually about half of this (0.12K). While still significant, it's not a doubling of the warming rate (which is around 0.19K per decade).
The forcing being equal to 80% of the heatuptake is also interesting, but we have not seen such a large step change in energy imbalance in the Earth system. This doesn't mean they are wrong about the forcing estimate, but it does not mean that 80% of the warming since 2020 has been due to ship fuel regulations either.
Water vapour is a very strong infrared absorber, so much so that it is more important for the greenhouse effect than CO2. However, it is usually very difficult to change the amount of water vapour in the atmosphere as a whole (it just rains out).
The stratosphere cycles through much slower than the troposphere (there are very few clouds, for example). That means that if you put water there, it can stay there for a lot longer, increasing the total amount of water in the atmosphere and warming the climate.
I'll also say that we expect water vapour to increase as temperature increases, which is a positive feedback in the climate system,increasing the warming beyond that of CO2.this is known as the water vapour feedback.
The increase in humidity is actually a different effect - evapotranspiration from trees is included in climate models (along with their response to increasing CO2 concentrations) [0].
The effect in this article is more to do with the particulates that form from the chemical emitted from trees. The article doesn't make it clear, but an increase in tree particulates (known as aerosols) would actually cause less rain.
Almost all cloud droplets form on an aerosol particle, so the cloud droplets in a cloud with more aerosols are on average smaller (as the water is spread out over more droplets). These smaller droplets take longer to grow large enough to form rain, an effect which is thought to decrease the amount of precipitation in some regions (although by a small amount).
This effect is also included in climate models, but the sources of aerosol (such as from trees) are more uncertain [1], producing the uncertainty in future climate projections.
[0] https://gmd.copernicus.org/articles/4/677/2011/gmd-4-677-201...
This is related to my reply above, but clouds in general move heat upwards in the atmosphere through latent heating.
When you evaporate water from the surface, you cool it (like sweating keeps you cool). This water vapour is then lifted by convection until it cools enough to condense and form a cloud. As the water vapour condenses, the opposite happens and it heats the atmosphere locally (this further invigorates the convection)
Once you have condensed enough water (and the water droplets/crystals are large enough), you form precipitation. This falls back to the surface (some evaporates along the way), where the process starts again.
This transporting of energy through the water cycle is an important component of how energy moves in the Earth system - you can see it on this figure as 'latent heating', moving energy away from the surface at something like 80Wm^-2
https://www.globalchange.gov/browse/multimedia/earth%E2%80%9...
Maybe I should describe my job differently...
It heats up the atmosphere and eventually gets emitted back into space!
For the Earth's temperature to remain approximately constant, the energy leaving the system (as infra-red) has to balance the energy entering the system (as sunlight).
The atmosphere is almost transparent to visible light, so sunlight doesn't really heat the atmosphere at all, it mostly heats the surface.
In contrast, the atmosphere is mostly opaque to infra-red (apart from the 'window region' at about 10um), which means energy is mostly emitted from higher levels in the atmosphere.
This means that you have to have a way of getting energy from the surface (were it effectively 'arrives') to higher levels in the atmosphere (where it can leave the Earth system again. Latent heat is an important way for this to happen - you can see it in this figure, showing how energy flows in the Earth system
https://www.globalchange.gov/browse/multimedia/earth%E2%80%9...
As a "cloud person", I just want to add a few things to the description of how clouds affect the climate (and why high clouds have a wamring effect).
All clouds are white, so they all reflect sunlight back into space (during the day), cooling the Earth.
All clouds are (almost) black in the infra-red, meaning the amount of energy they emit in the infra-red is determined by their temperature. Colder clouds emit less energy.
Almost all clouds are colder than the surface beneath them, which means they emit less infra-red energy to space than a clear day would. This reduces the amount of energy the Earth emits to space, so warming the climate.
High clouds are colder than low clouds, so have a stronger warming effect.
In summary:
Low clouds - Reflect sunlight (cooling), don't trap much infra-red (little warming)- Net: Cooling effect
High clouds - Reflect sunlight (cooling), trap lots of infra-red (stronger warming) - Net: Warming effect
The PR part also applies to Earth Observation Satellites (ESA and EUMETSAT). (Almost) any time you see a wide area picture of the Earth from Space (particularly around a weather event), it comes from NASA's MODIS instrument [e.g. 0].
The European (approximate) equivalent, AATSR, had a lot of really nice scientific qualities, but it was missing a blue channel, meaning that the 'true-colour' images it produced always had a blue tint to the clouds. There was a similar problem with the European geostationary satellite imager (SEVIRI) [1].
Scientifically, SEVIRI was incredibly useful (and far in advance of the American equivalent at the time), but the lack of a blue channel meant that it was never really used for those shots that made it onto the news (and neither was AATSR). When you have spent multiple billions on a satellite programme, you generally want the public to see it.
I remember being told at one point that this was considered such an issue that the Europeans would 'never launch a satellite without a blue channel again' - although that might be overstating it a little.
I thought that aircraft could use much more than 5%, but that the maintenance regime was different - e.g. [1]. Current engines assume a proportion of impurities and are tuned to work with that, but could be modified to run with 100% SAF if it was available.
Just to add - 10% increase on the state of the art is nothing small!
[1] https://www.gov.uk/government/news/royal-air-force-completes...
I suspect it will at least be publicly available, although there might be some terms attached (I don't know).
SEVIRI (the current instrument) has data available through the EUMETSAT data store. It was a while since I registered, but it was at least free for personal/educational/research use at that point.
edit to add - the current iamgery is also available here [2]. Excellent if you want some psycadellic composite imagery. Day microphysics is a personal favourite, although I am biased... [3]
[1] https://data.eumetsat.int/extended?query=High%20Rate%20SEVIR...
[2] https://eumetview.eumetsat.int/static-images/latestImages.ht...
[3] https://eumetview.eumetsat.int/static-images/MSG/RGB/MICROPH...
The new imager (FCI) will be fantastic for studying the atmosphere, particularly clouds and aerosols (like desert dust).
The older imager (SEVIRI) didn't have a blue channel, so all the true-colour images have to be synthesised from data at other wavelengths, giving some of the clouds a characteristic light blue shine. FCI doesn't have that issue, meaning that it can create better 'true-colour images'. It actually has a real green channel too (unlike the GOES ABI instrument), although the iamges from both look brilliant.
This blue channel doesn't just help make images look nice, it is also important for measuring aerosols like dust. At blue wavelengths, the surface tends to be much darker, meaning that you can measure aerosols over even relatively bright surfaces (like deserts). With the Sahara looming pretty large in the image, you can see why that might be important! [1]
FCI also has some high resolution near-IR channels (including the 2.3 one at 500m resolution). This is fantastic for studying clouds, as the reflectivity of clouds at this wavelength allows you to measure droplet size (which is important for understanding cloud processes) [2]. Very few other instruments have this capability, and none of the existing geostationary satellites do (obviously other than MTG).
[1] https://earth.gsfc.nasa.gov/climate/data/deep-blue/science
There were a few Earth Observation missions that didn't make orbit about 10-15 years ago. This was due to a failure of the Taurus-XL fairing separation.
The orbiting carbon observatory (OCO) failed to reach orbit in 2009 [1]. It got a replacement (a good thing, given how important these measurements are.
Glory [2] would have had a really cool polarimiter (measuring light polariasation as well as radiance, in a range of different directions, but it failed in 2011 for the same reason as OCO. Unfortunately, it didn't get a replacement.
[1] https://en.wikipedia.org/wiki/Orbiting_Carbon_Observatory
Organisations aiming to reduce sulpfur in ship fuel are defiitly aware of the cooling impact it has on the climate. However, the health benefits of this reduction are not to be understated - with shipping sulfur being responsible for 100s of thousands of premature deaths and millions of cases of childhood astham annually [1].
The cooling effect from ship pollution is there, but it is a relatively small fraction of the ovrall cooling from atmospheric aerosols.
[1] - Sofiev et al, Cleaner fuels for ships provide public health benefits with climate tradeoffs - http://dx.doi.org/10.1038/s41467-017-02774-9
Another way to think about it is in terms of average person years
American: ~15 tonnes CO2 per year - 126 years
European: ~10 tonnes CO2 per year - 190 years
World average: ~5 tonnes CO2 per year - 379 years
I don't think this accounts for non-CO2 impacts either (e.g. contrails). Multiply the years by about 2 as an estimate of that.
I understand where you are coming from and agree that we need to know more about this to do it properly if required. However, I think some of this reflex is jusified by the known side-effects (not even the potential unintended consequences).
Greenhouse gases heat the surface and the atmosphere, but solar radiation management (SRM) mostly cools the surface. If you use SRM to get the surface temperature 'right' that atmoshpere is still warmer that it would have been. This means you get less rain. Many places care more about rain than temperature.
This is a well understood consequence, but the specifics are where it gets very tricky. There is a non-zero chance that using SRM to cool the planet may also kill the Amazon rainforest by reducing rainfall. This obviously makes things a whole lot worse and no longer buys us time. [0]
This is not even an unknown unintendend consquence, it is pretty clear already. Obviously this doesn't mean we shouldn't look into it, but we already know the consequences of geoengineering are ... not good.
[0] https://acp.copernicus.org/articles/12/10887/2012/acp-12-108...
Just to add that the majority of geoengineering methods currently proposed - particularly those that reduce absorbed solar radiation (such as stratospheric sulfate and marine cloud brightening) come with some significant side-effects.
Many proposed geoeningeering methods don't treat the problem but just mask the symptoms. For starters, CO2 heats the surface and the atmosphere, but solar radiation primarily heats the surface.
This means you cannot use a reduction in incoming sunlight to fully offset CO2 warming - if you get the surface temperature correct, the atmosphere is still warmer and so you get less rain. For many regions, a reduction on rain might be more important - we wouldn't want to end up killing the Amazon rainforest by accident!
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2008JD01...
Water provides the 'energy' that drives many storms. As a bubble (or parcel) or air rises, it cools. Eventually it gets cold enough to condense water (some of which forms rain). This heats the parcel of air, making it less dense than it was and so more buoyant - so it rises faster and invigorates the cloud/storm.
If you have more water around, this process is stronger (as you have more available water to condense and energise the storm), eventually producing more rain.
This is the reason why you see the biggest thunderstorms in the tropics, where it is warm and moist.
I am not entirely sure what a cliamte change absolutist is, but have you thought of the possibility they might be right?
Obviously we have had extreme weather before, but many of the extremes we are seeing now are far, far outside normal (in some cases more than 100 times as common).
You might feel that every time an event comes up in the media, it is claimed it is because of climate change. Perhaps most of these extreme events are (or are at last much more common)?
We already know that climate change has an outsided impact on extreme events, particularly heatwaves, making them hotter, longer and more frequent. Many of these physics principles apply worldwide, so we end up seeing the fingerprint of cliamte change in extreme heatwaves across the world.
Media focus does play a role, but weather records from many parts of the world go back over 100 years. These are independent of what the media is focussing on today and give us a very good picture of whether a particular weather event is 'extreme' or not.
These events really are exceptional. As an example, last month the UK temperature record was broken by over 1C, across large regions of the country. Usually, temperature records are broken by small amounts, maybe 0.2C. This heatwave really was extreme for the UK.
7 out of 10 of the hottest days in UK history have been since the year 2000. In a country with particularly long temperature records, this is also pretty amazing, and evidence of a significant change in the cliamte and extreme events.
I think there is one extra point though - that these events can be much, much more frequent.
When an event is 100 times more likely, you are getting very close to a 'caused by' situation.
Obviously, extreme events existed in the past. But something like the 2022 south Asia heatwave was so extraordinarily rare before, when climate change increased the frequency of similar events by more than 100 times, climate change was responsible (in most reasonable uses of the word).
https://www.metoffice.gov.uk/about-us/press-office/news/weat...
Yes, there were extreme events in the past. These events are now much more frequent thanks to climate change. Sometimes 10s to 100s of times more common.
Gloal climate change is caused by human emissions of greenhouse gases. This is now very clear and there is very little evidence of anything else having more than a small impact.
The COVID lockdowns had an effect on the climate, see for example the reduction in high clouds due to a decrease in flying [0]. Stopping GHG emissions only prevents further climate change. It does not fix it, just stops it from getting worse.
To change the climate 'back', we have to remove CO2 from the atmosphere, not just stop emitting it.
Many people who want to stop climate change are also pro nuclear energy as a means of doing that. But why would that have anything to do with redistribution of the means of production?
[0] https://iopscience.iop.org/article/10.1088/1748-9326/abf686
You could try the Met Office website. This is a station in North West London
https://www.metoffice.gov.uk/weather/observations/gcpvj0v07
Humidity was about 15-20% during the afternoon, winds 13 gusting 26mph.
Some of the side effects are common to all kinds of solar radiation management (SRM) - geoengineering that makes the Earth more reflective in some way or another.
Greenhouse gases absorb infrared radiation emitted by the Earth and heat the atmosphere as well as the surface. SRM geoengineering just changes how much energy the Earth absorbs from the sun (which has the strongest effect at the surface).
If GHGs increase, but you use SRM to keep the surface temperature fixed, you still end up heating the atmosphere. This means in a geoengineered world, you have less rain.
A reduction in rain might be more important to some countries than others - not everyone would want the same amount of geoengineering.