At the uks hottest weather station, ill discover how you go about accurately recording temperature, and ill be finding out whats behind another year of record heatwaves. The science is overwhelmingly clear that the cause of this Climate Change is our activities as humans putting more and more Carbon Dioxide and other Greenhouse Gases into the atmosphere. And im at Cambridge University, where a new look at pioneering Data Collected in the 1970s is revealing the real impact Climate Change is having on our melting ice sheet today. Also on weather world, 2019s biggest storms, from devastation in the bahamas, hit by its most powerful hurricane, to the fire ravaging parts of our world. And climates in crisis as a swedish teenager becomes the face of public protest. How the 2010s became a decade like no other for our climate. Cambridge, famous for its university, its scientists, its punting on the river, and now its heat because of this. This weather station, which onjuly the 25th 2019 of 38. 7 degrees celsius. Now, in a year when Climate Change has become increasingly labelled a climate crisis, that may be an unwanted accolade, but nonetheless its a record that now cambridge holds. But how do you go about verifying a temperature like that, accepting it in a National Record . Well, philjohnson from the met office was involved in that process on that day. Phil, tell me what you did. Well, hi, nick. Well, first of all we had a good indication that record temperatures would be broken. From there we could actually start monitoring temperatures in real time. However, part of our network is done by volunteers such as at Cambridge UniversityBotanic Garden. And so it wasnt until the following day where we heard that the temperature had been broken. We needed to come in here and first of all check that the actual instrument had been read correctly. Then we performed a comparison or verification with a precision thermometer to make sure the instrument was actually performing correctly. And in addition, we needed to check the environment, the surroundings where the screen is. And is the instrument actually deployed correctly . Is it exposed correctly . And there is a thermometer inside this box. But tell me why its enclosed like this. We want to measure the air temperature. If the thermometer was actually outside, then well be heating the thermometer directly from the sun, and so that would give a false reading, the same as if you put a thermometer on the wall, youre actually measuring the temperature of the wall and not the air temperature. And theres a very good reason you dont want to open this box today to show us the thermometer inside. Its a very, very sensitive piece of equipment. As soon as we open the door, we actually may get a little spike in the temperature, which we cant accept for our readings. And the principles of recording heat like this are the same anywhere in the world. Indeed, the World Meteorological organization, they provide standards where we should measure temperatures. For the met office our standard is 125 centimetres above ground level, normally above grass, some countries are a little bit higher, but generally we are within their guidelines. Phil, really good to talk to you. Thank you. And it wasntjust in the uk that heat was hitting the headlines in 2019, farfrom it. Australia in november, and its largest city, sydney, is almost lost in smoke as multiple fires burn in dry, hot, windy conditions, producing catastrophic fire danger. Firefighters face near impossible conditions as temperatures soar. And worse is to come in december, as the country endures its hottest day on record. In august, the world watched as a Record Number of wildfires burned in the amazon amid a political storm about blame. In the usa in october, californias largest fire of the season so far rages north of san francisco. Earlier injune, the city had its hottest three days ever recorded in summer. And it was a series of astonishing summer heatwaves in europe that shattered records across multiple countries, including here in france injune, as the temperature reached nearly 46 celsius. Then injuly, new National Records were set in germany, belgium, the netherlands and the uk. And as the year came to a close, the World Meteorological organization said the last decade was set to be the planets hottest on record. Joining me now to talk about all things heat here at Cambridge UniversityBotanic Garden is dr emily shuckburgh, Cambridge Universitys chief climate scientist. So what stands out for you from whats been happening heatwise around the world in 2019 . Well, i think obviously what stands out for me beyond all else is the record temperatures that were recorded here in these gardens back in the summer. 38. 7 degrees celsius. And the really significant thing about heat of that level, though, is the effect that it has on peoples lives and particularly on vulnerable people, either the very young or the very old. And weve seen spikes in death rates particularly amongst the elderly in the heatwaves that weve seen in recent years. And thats a significant concern. And in terms of those record temperatures and how they fit into the heatwaves, is that something which is going to happen more frequently, or is already happening more frequently . We are seeing it already. So heatwaves in some parts of the world that used to happen maybe a couple of times a century before any Climate Change, were now seeing it occurring every few years. And as the temperatures increase globally, those frequencies will increase still further. Whats driving the heat and the increasing heat that were getting . The science is overwhelmingly clear that the cause of this Climate Change is our activities as humans putting more and more Carbon Dioxide and other Greenhouse Gases into the atmosphere. So, today our Carbon Dioxide levels are coming close to being 50 higher than they were before the start of the industrial revolution. And that has driven globally temperatures to be more than one degree celsius warmer than that time. And that might sound like quite a small number, but the implications of that are really significant increases in the risk of extreme weather events. Good to talk to you. Well be back with you again later in the programme. Now its time to cross to sarah, whos looking at whats going on with temperatures at the other end of the extreme. A warming world is still capable of extreme cold and back injanuary 2019 in the usa, chicago recorded its lowest temperature in 3a years, with minus 30 degrees celsius. You see this on my glasses . This is notjust fog, but frost. Its ridiculous out here, and its going to get worse. Where you expect it to be cold, temperatures are on the rise. In fact, the arctic is warming twice as fast as the rest of the planet, and in 2019 recorded its second smallest sea ice extent in the satellite era. But the arctic hit the headlines for Something Else in 2019. Fire. Millions of hectares of forest burned within the Arctic Circle in scenes described by experts as unprecedented. Higher temperatures and a greater frequency of lightning are partly to blame. In order to better understand whats been happening in our polar regions during 2019, ive come here to the Scott Polar Research institute at the university of cambridge. Its the oldest dedicated Polar Research institute in the world. And professor Julian Dowdeswell is the director. So, julian, tell me a little bit about the work that goes on here. Our main expertise, i suppose, of where we put most of our resource is what we call the icy world and in particular, ice and environmental change. And, of course, a huge amount has changed since captain scott, shackleton and Edward Wilson first went into the interior of antarctica. Scotts First Expedition collected over 20 volumes of data concerning the antarctic at that time, which provides arguably the earliest baseline against which we can judge contemporary change in that part of the polar regions. And over that hundred years, how has our perception of and our relationship with the polar regions changed, because theyre very much at the forefront of our minds these days . When i started in the field as a doctoral student a0 years or so ago now, people thought that the polar regions were interesting, but a little bit divorced from the rest of the world, indeed from the rest of the Global Climate system. And now, of course, we know that absolutely is not the case. And indeed both the arctic and the antarctic are major drivers of the growth of the Global Climate system. And indeed both the arctic and the antarctic are major drivers of the growth of the Global Climate system. The poles are just about as far away as you can get from the big, industrial, carbon emitting parts of the world. So why is it that the poles are quite so sensitive to Climate Change . The arctic is almost inarguably the most sensitive part of the whole Global Climate system. But in the last 20 or 30 years, theres been an enormous change in the summer sea ice cover in the arctic. In fact, a change from about eight million Square Kilometres per year to only about four and a half or 5. And what you do by removing that ice by the end of the summer, because its slightly warmer in the arctic, is you change the reflectance of the surface very greatly, and you swap something thats very bright and reflective for something thats much more like myjumper, for something thats really absorbent. That happens year on year. Each year, theres a bit less sea ice. The temperature is, of the water in particular, just a fraction warmer, which makes it more difficult the next year for the sea ice to form, thats a self reinforcing process. And that is the reason really that ice reflectance, that feedback, that is the main reason why the arctic is the most sensitive part of the whole Global Climate system. And 2019 has been another year of extreme weather around the world, from record breaking heatwaves, floods and also wildfires even to the north of the Arctic Circle. So what really stands out in 2019 in terms of whats going on at the poles . Fires are a big thing throughout the globe. And, of course, they manifest themselves by things like black carbon in ice cores. And we can actually trace how those have changed over the decades. Over the past 800,000 years in the longest Antarctic Ice cores, we can see that co2 levels are very strongly coupled with temperature over successive glacial, interglacial cycles. Thank you so much, julian. And thinking about how we use historic ice data to look forward into the future, a little bit later in the programme ill be back looking at some newly available digitised ice data that is helping climate scientists map what could potentially happen to our climate in the future. Now for some of your weather watcher pictures, starting with these scenes from november when parts of england suffered severe flooding in a deluge which contributed to south yorkshire, nottinghamshire and lincolnshire seeing their wettest autumn on record. But the autumn rainfall wasnt evenly distributed across the uk. In fact, parts of northern and western scotland were much drier than average in autumn and exceptionally dry in november. Become a bbc weather watcher by signing up online at bbc. Co. Uk weatherwatchers, and you could be in the running for pic of the season, which in autumn was won by tonys view of the stormy seas in wales. Still to come on weather world underwater why a warmer world could also mean a wetter world. Now on weather world, some of 2019s biggest storms, starting with Hurricane Dorian seen approaching the bahamas in september. The few images taken as the category five storm hit paint a terrifying picture as a flooding storm surge ploughs across the abaco islands. The aftermath is apocalyptic. The near complete devastation here at Marsh Harbour on great abaco is a product of the strongest storm ever to have hit the bahamas and one of the most powerful on record in the atlantic. In the western pacific in october, hagibis is the strongest typhoon in 60 years to hitjapan. The storm leaves behind widespread damage, including to these bullet trains swamped by the floodwaters. Earlier in march, cyclone idai is one of the strongest ever to hit africa. This is what it did to the city of beira in mozambique. Idai is the southern hemispheres second deadliest Tropical Cyclone on record. And in may, cyclone fani ploughs into the east coast of india. Its the strongest storm here in 20 years. But countless lives were saved thanks to a Mass Evacuation in advance of the storm. No Tropical Cyclone in italy, but a storm surge all the same combines with the venice high tide in november to produce the worst flooding here in over 50 years. St marks basilica was said to have suffered grave damage with its crypt completely flooded. In the uk, 2019 has brought bouts of severe flooding, most recently in november across parts of yorkshire and the midlands as record autumn rainfall sent some rivers to their highest levels ever recorded. Chanting during 2019, public protest and direct action about Climate Change reached new levels. Spain in december, and thousands demonstrate as madrid hosts the United Nations climate conference. Arriving by train, teenage Swedish Environmental activist Greta Thunberg has a police escort, such is the interest in someone whos become the face of the climate protest movement. Addressing the conference, she said not enough is being done to combat the climate crisis. To stay below 1. 5 degrees, we need to keep the carbon in the ground. 0nly setting up distant dates and saying things which give the impression that action is under way will most likely do more harm than good, because the changes required are still nowhere in sight. Well, im back here at Cambridge Universitys Botanic Garden with Cambridge Universitys chief climate scientist, dr emily shuckburgh. Emily, we talked earlier about how warm the world has become. But in that video, we saw lots of rain and flooding. So how does this warmer, wetter world fit together . Yes, it might sound counter intuitive, mightnt it . But, actually, a warmer atmosphere can hold more water in it. Thats just simple physics as to how that happens. And that means that theres more, that its wetter, essentially, to be able to rain down and heavy rainfall events. And thats the essential reason why weve seen more and more flooding here in the uk, but also flooding events around the world as well. And weve seen really powerful hurricanes and typhoons as well. Is that something that also fits into Climate Change science . Mm, the way in which Climate Change interacts with hurricanes and cyclones is quite complex. But in terms of the damage caused by those hurricanes and cyclones, its very clear that much of that damage is exacerbated by Climate Change. So weve just talked about how Climate Change can cause heavier rainfall and a lot of the damage associated with cyclones, this comes from the flooding, the storm surges that weve seen associated with those. So heavier rainfall, greater storm surges, but also Sea Level Rise across the world. As the seas have been rising, those storms are going to penetrate and amidst all of that background of heat, flooding and storms, 2019 has really been a year of political activism, public activism as well when it comes to Climate Change, more awareness about that, hasnt it . Weve seen young people around the world really rising up and saying that our future is at stake and their future really is at stake. Its decisions that we all make over the coming decade that will determine notjust our childrens future, but their grandchildrens and their grandchildrens future as well. Thanks for talking to us in this lovely setting on such a sunny day. Thank you a uk climate scientist and his team at Reading University are helping us to visualise how much the world is warming with these climate stripes here showing each years average Global Temperatures since the 1880s in a coloured stripe, clearly progressing from blue to red over time as temperatures have warmed. Bbc weather presenter ben rich takes a look at how you can look for a climate stripe to show the temperature trends where you are. This is the show your stripes website, and on the home page, were greeted by the same Global Climate stripes weve just been looking at. But the great thing about this website is we can delve a little deeper. We can look at patterns in different places around the world. And its quite simple to