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YouTube has removed the dislike counter but the numbers are still available backstage and I can tell you that my most disliked videos by far are those on climate change doesn't matter if it's
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good news or bad news some people it seems reflexively dislike anything about the topic every time and to be honest I can kind of understand that it's a
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little tiresome isn't it climate change extreme weather heat records blah blah blah we've heard this for so long and look we're still here stop talking about it already I get it and I'd rather just
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talk about some fun new physics stuff but I feel like I need to tell you about this because the lives of hundreds of millions of people depend on it climate scientists are having an argument about
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a number one single number called the climate Sensitivity I don't like what I've read it really worries me and I think you should know I know you expect me to be funny haha not funny peculiar
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but I'm afraid this video will be more on the peculiar side why does Sabina worry about climate change and why now that's what we'll talk about today this video comes with a quiz that
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lets you check how much you remember 2023 was the hottest year on record since the beginning of Records in the mid 19th century not just the average temper increased to neverbe seen levels
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in many places heat waves were also longer and hotter than ever before in February Antarctic sea ice reached an absolute record low since the beginning of satellite measurements in
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1979 and Global ocean temperatures reached a new record too I don't know about you but to me that sounds pretty bad now it's possible that 2023 was somewhat of an outlier and average
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temperatures will somewhat decrease in the next three years there are several reasons for this first there's just regression to the mean but second there's also that in 2023 we switched
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from a linia to an ELO phase the Lin ELO phases are Quasi periodic Global Climate patterns these phases switch somewhat irregularly but roughly every 2 to three years and the N phase that we just
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switched to is typically somewhat warmer so next year might break more records because it will still be alinu but in 2 to three years we might see a slight Cooling and third some researchers have
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speculated that part of this year's warming might have to do with the decrease in pollution over the oceans caused by new regulations of ship exhausts it's somewhat unclear how large
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this effect is but we do know that air pollution does indeed have a cooling effect so maybe that's part of the reason be that as it it may I worry that even if 2024 is not a new record breaker
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the overall trend in the next few years will be steeply up and the situation is going to deteriorate rapidly the reason is to do with a quantity called climate sensitivity climate sensitivity contrary
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to what you might think is not what makes people hit dislike on climate change videos it's a property of climate models it's the temperature change that one finds in a model when one doubles
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atmospheric carbon dioxide over the levels of pre-industrial times and then waits for the system to come into equilibrium in the literature it's called the equilibrium climate
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sensitivity ECS for short this equilibrium climate sensitivity isn't something we directly observe because no matter how much they dig in Saudi Arabia in reality carbon dioxide levels don't
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suddenly Jump by a factor two however it's a useful quantity to gauge how how strongly a model will react to changes in carbon dioxide and this climate sensitivity is the key quantity that
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determines the predictions for how fast temperatures are going to rise if we continue increasing carbon dioxide levels up to 2019 or so the climate sensitivity of the world's most
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sophisticated climate models was roughly between 2 and 4.5 de C these big climate models are collected in a set that's called the coupled model inter
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comparison project seip for short that's about 50 to 60 models and is what the ipcc reports are based on so until a few years ago we had a climate sensitivity
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of 2 to 4.5 de or so and that's what we came to work with that's what all our plants rely on if you can even call them plants you've probably all seen this range in the ipcc projections for the
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temperature increase in different emission scenarios it's this shap ated region around the mean value Loosely speaking the lowest end is the lowest climate sensitivity the highest end is
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the highest climate sensitivity then this happened in the 2019 model assessment 10 out of 55 of the models had a climate sensitivity higher than 5° C that was well outside the range that
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was previously considered likely if this number was correct it would basically mean that the situation on our planet would go to hell twice as fast as we expected okay you might say but that was
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5 years ago so why haven't we ever heard of this what's happened is that climate scientists decided there must be something wrong with those models which gave the higher climate sensitivity they
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thought the new predictions should agree with the old ones in the literature they dted the hot model problem and climate scientists argue that these hot models are unrealistic because such a High
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climate sensitivity isn't compatible with historical data this historical data covers many different periods and reaches back to a few million years ago back then when we still used D up modems
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it's called the paleoclimate data of course we don't have temperature readings from back then but there's lots of indirect climate data in Old samples from rocks I fossils and so on in 2020 a
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massive study compiled all this paleo climate data and found that it fits with a climate sensitivity between 2.6 and 3.9 de C and this means implicitly that
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the hot models the ones with the high climate sensitivity are not compatible with this historical data as a consequence the new ipcc reports now weigh the relevance of climate models by
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how well the models fit the historical data so the models with the high climate sensitivity contribute less to the uncertainty which is why it has barely changed and that sounded reasonable to
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me at first because if a model doesn't match with past records there's something wrong with it makes sense then I learned the following the major difference between these hot models and
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the rest of the pack is how they describe the physical processes that are going on in clouds a particular headache with clouds is the super cool phase of water that's when water is below the
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freezing point but remains liquid the issue is that the reflectivity of the clouds depends on whether it's liquid or not and that super cooling makes the question just exactly what influence the
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clouds have very complicated but how much data do we have about how clouds behaved a million years ago as you certainly know the dinosaurs forgot to back up their satellite images so
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unfortunately all that milliony year old cloud data got lost and we don't have any to use the argument from historical data therefore climate scientists must assume that a model that is good for
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clouds in the current climate was also good for clouds back then under possibly very different circumstances without any direct data to check that seems to me a very big if given that getting the
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clouds right is exactly the problem with those models wouldn't it be much better to check how well those models work with clouds for which we do have observations like you know the ones that we see in
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the sky in principle yes in practice it's difficult that's because most climate models aren't any good as weather models while the physics is the same they're designed to run on
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completely different time scales you make a weather forecast two weeks at most but climate models you want them to run a 100 years into the future there's one exception to this there's one of the
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hot climate models that can also be used as a weather model with only slight adaptations it's the one from the UK Met Office so a small group from the UK Met Office went and used this hot model to
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make a 6-hour weather forecast they compared the forecast from the hot model with the forecast from an older version of the same model that didn't have the changes in the cloud physics and was
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somewhat colder they found that the newer model the hotter one gave the better forecast And just so we're on the same page when I say the forecast was better I don't mean it was all sunny I
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mean it agreed better with what actually happened and that model with the better predictions had a climate sensitivity of more than 5° C I know this all sounds
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rather academic so let me try to put this into context the CL climate sensitivity determines how fast some regions of our planet will become uninhabitable if we continue pumping
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carbon dioxide into the atmosphere the regions to be affected first and most severely are those around the equator in central Africa India and South America that's some of the most densely
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populated regions of the world the lives of the people who live there depend on that scienti get this number right so we need this number to get a realistic idea
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of how fast we need to act that the climate sensitivity might be considerably higher than most current policies assume is a big problem why wasn't this front page news Well quite
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possibly because no one read the paper I didn't either as of date it's been cited a total of 13 times I only know about this because my friend and colleague Tim Palmer wrote a comment for nature
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magazine in which he drew attention to this result he also asked other researchers to try and do similar tests with other models to see how well they perform with the short-term weather
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forecast unfortunately no one listened to him that includes me because I have better things to do than read all of Tim's comments sorry Tim and in all honesty I had pretty much forgotten
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about this but then late last year a new paper with Jim Hansen's lead author appeared which reminded me of this the new hanset all paper is a reanalysis of
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the historical climate data in a nure they claim that the historical data is compatible with the climate sensitivity of 4.8 plusus 1.2 de Celsius that agrees
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with the hot models and if it was right it would invalidate the reason that climate scientists had to dismiss the models with a higher climate Sensitivity I don't want to withhold from you that some some climate scientists have
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criticized the new hanset or paper they have called it a worst case scenario that is quite subjective and not justified by observations model studies or literature though it isn't irrelevant
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to note that the person who said this is one of the authors of the previous paper that claimed the climate sensitivity from historical data is lower I don't know who's right or wrong but for me the
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bottom line is that the possibility of a high climate sensitivity above 5° C can't be easily dismissed especially not seeing how fast average temperatures
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have been rising in recent years and that's really bad news because if the climate sensitivity is indeed that high then we have maybe 20 years or so until our economies collapse and what's the
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point of being successful on YouTube if my pension savings will evaporate before I even retire yeah yeah that's a t bit depressing but if you want to hear an uplifting story about Environmental
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Protection stay around until the end because I want to tell you about my friends at Planet wild this isn't in the script but it just blows my mind how
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mind fuckingly stupid it is that the lives of all people on this planet depend on an obscure discussion about the properties of super cool water
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droplets in a type of cloud whose name I can't even remember and that returns me to the people who reflexively dislike any video on climate change because they really really don't want to hear about
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it I believe that most of them aren't actually climate change deniers I think they just can't see how it's going to affect them what's the big deal with the few degrees temperature increase we just
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turn up the air conditioning right I think it won't be that easy which is why I now want to spend a few minutes telling you what I think will happen in the next 20 years or so the next minutes
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of this video will be quite depressing and if you're struggling with anxiety I sincerely think it would be better if you stopped watching here did I just tell people to not watch my videos I'm
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not doing this YouTube thing right am I if you're still with me here we go Earth has five different climate zones and each has its own typical type of vegetation if climatic conditions change
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rapidly a lot of plants will not grow properly or die because it's too hot or too dry or too wet or all of the above yes plants like carbon dioxide but that isn't going to make up for the much
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bigger problem of the rapidly shifting climate zones and yes we can try to genetically engineer plants that are better adapted to the new circumstances but that's going to take time and time
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is exactly what we don't have if the climate sensitivity is really as high as the hot models say people in the developed World somehow cope with the hotter conditions by fertilizing and
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irrigating the hell out of any agricultural areas they have but in many countries around the equator crop yield will substantially drop this will most affect countries that are already prone
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to famine and at the same time some of the poorest countries in the world will be hit very hard by heat waves and drought I don't think that a human right for air conditioning that some people
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argued for in a Scientific American article is going to make much of a difference okay so we have femine and drought and heat waves but it's just you know we're poor people live it isn't
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really our problem right well that's not the end of the story because those poor people who don't con conveniently die right away will draw consequences they'll leave we're talking about some
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hundred millions of people who have nothing left to lose suddenly beginning to migrate where they go most of them will go north why just because there's
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more land north of the equator than South that's going to cause a lot of tensions at the southern borders of Europe Russia and Mexico for just to mention a few someone somewhere will
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make a lot of money by selling weapons drones will be deployed some of them will shoot innocent people will die but wait that's not it because death and migration make a great breeding ground
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for new viruses bacteria and fungi so chances are we're going to get a new pandemic along with it so we have widespread crop failure High numbers of people dead Mass migration political
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tensions and possibly War likely Public Health disasters meanwhile people in the developed world are scrambling to adapt moving Inland our sea water levels continue to rise trying
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to install air conditioning wherever they can and are giving up pretending to cut back carbon dioxide emissions which is going to speed up the further proceedings the result will be an
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enormous economic downturn the Practical consequences for you and I will be that everyday products will become more and more expensive until most of us simply can't afford them anymore and then
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they'll disappear need a new phone that'll be $50,000 internet connection at home $8,000 a month want a new microwave sorry we're all out of stock need
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someone to fix your roof we're short on staff they are still cleaning up the mess from the recent flood in simple terms the problem is that there's only so so much work one person can do in one
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day and if we're busy trying to survive everything else would go on PA people who are busy building air conditioning units are people who are not pushing The Cutting Edge of nanotechnology I don't think we'll go
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extinct there's just too many of us and I don't think civilization will entirely collapse because much of the infrastructure we already have is going to last until the worst is over but it's
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going to be a phase of regress rather than the progress that we've become used to it's going to be really unpleasant will quite possibly reduce the world population by a few billion and it's not
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a world that I want to live in and no AI isn't going to solve the problem because the problem isn't that we're missing a technological solution the problem is that we can't agree to implement the
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solutions that we have you probably expect me to end on some recommendations I don't think it matters much what I recommend but I also don't want you to go away complaining that I
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haven't thought about it so here's my wish list put a price on carbon dioxide emissions now continue to expand Renewables build nuclear build nuclear
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build nuclear stop bitching about carbon dioxide removal there's no way around it and For Heaven's Sake stop gluing yourself to things now I'm not asking you to like this video I don't really
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like it myself but then let me tell you about something that I do like that's my friends at Planet wild who are saving this planet one step at a time Planet wild is a community-based Environmental
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Protection Organization they're funding the restoration of ecosystems to preserve our nature and Wildlife I've been part of their Community since earlier this year and I've been really
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impressed by their work they select a new partner every month and they document their missions with video reports that you can find right here on YouTube this way you get to immediately
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see the impact of your contribution for example they've repopulated a forest in Germany with the Eurasian links and in their latest Mission they've gone to cap ver to protect sea turtles from poachers
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with the help of dogs it's such a lovely Hands-On approach and it really makes a difference all of this is made possible by a community that funds these projects a community of nature enthusiasts like
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you and I one person doesn't have a lot of impact on the environment but bundling resources of a community can achieve a lot what I find so great about Planet W is that they don't leave me
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wondering where my money goes you can become a nature supporter for as little as $6 a month that doesn't even buy you a sandwich at heo and don't worry that you'll get stuck with them you can
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cancel your membership every month I support Planet wild because I can see it has a direct impact on preserving nature and protecting our EOS systems if you want to join a growing community that
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makes a real difference go check out Planet wild through the link in the description or by scanning the QR code and consider becoming a supporter I'll cover the first month of your
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subscription if you're among the first 200 people signing up with the code zabina thanks for watching see you [Music] [Applause]
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tomorrow
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