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another 5 days. germany has held an official ceremony to mark the 30th anniversary of its reunification president frank. addressed the event in potsdam you know berlin he described the past 30 years as a triumph of democracy of oppression he also warned against populism and extremist . sudan's transitional government and rebel groups have signed the landmark peace deal and in decades of war that has killed thousands you freeman signed in neighboring south sudan he called couples power sharing between the warring groups the return of refugees and land rights. this is d.w. news from berlin you can follow us on twitter and instagram at the deadly news or visit our website that's d.w. dot com.

well blue planet is becoming increasingly dominated by concrete over health the global population now lives in cities and the number is rising. not only are millions of people moving into urban areas wild animals are entire populations of them. urban areas are covered in cement bricks and asphalt which in harsh weather turns them into hot spots literally. and that's a good look at the rising temperatures in our cities welcome to tomorrow today the science show on d w. in the northern hemisphere is 2nd hottest summer since records began is just coming to an end. in the last 140 years there's only been one summer hotter than this 12016 that's here august

was particularly roasting the fall of hottest summers when the last 5 years climate change is catching up with us it's particularly evident in cities because they become heat islands. and heating is the name given to the so-called heat island effect temperatures and towns and cities broadens more sharply than in the surrounding areas because of the density of streets and buildings and the many people cars and trains all of which produce heat. spread over the year the mean air temperature in in the urban areas is around $1.00 to $3.00 degrees celsius warmer than areas outside of them or large spaces within them . on top of this town and city centers often cool down fall less at night because the building density doesn't allow cool air to. around the city. on

hot summer nights with out of 3 the temperature difference between a city and its surrounding can be more than 10 degrees celsius. what's needed is cool air from the surrounding area but what happens when a current of air meets an obstacle that's would under way as well be in this researching with the help of water light shining on tiny white particles suspended in the water reveals currents in the tank. here the current flows unhindered but then it hits a building. you can see there in front of it that there's turbulence and the current flows over the top of the building and there's more turbulence behind it and this is what happens when an air current is confronted with a building this is just one building but in a city up there are lots of them and that means all kinds of air currents. through mix. does cold air flow over

a building or around it and what happens if there are obstacles in its path rubin illuminates these issues too. if a building faces the wind its width and height are the key factors in blocking the flow of air. the bigger it is the more the current is blocked or. if i add another obstacle behind the 1st one that creates an area between them that is poorly ventilated. the wind if it only comes from the front goes over the top of both buildings. in the area between them remains poorly ventilated. but you can reduce this effect if you place the building with its narrow side facing the wind. that reduces the surface area the wind hits and allows it to flow passage of the building. with.

urban planners need to pay close attention to the orientation of buildings relative to prevailing winds here for example they block cool air coming off the high ground into the valley but if they're turned 90 degrees the wind passes between them and everything gets nicely ventilated. high rise buildings can also do their part in ventilating a city. although if i place a tall building behind a short one. the wind goes over the top of the short one and blows down into the street in front of the top and swirls around. you can influence the exchange of air in a city quite well pending on where the building stand relative to each other.

if the tall building is right in front of the short one that blocks the breeze and prevents cooling but if the distance is great enough that current also reaches the short building. big gaps between city buildings are read this proximity makes them he said and some cities like chennai and mumbai in india can reach 30 degrees celsius. lagos in nigeria is also one of the world's fattest cities. as is measured in saudi arabia. and he's saying is happening across the globe even in cooler places like the german capital them. joke forms is an urban climate expert searching for effective ways to reduce city temperatures this detailed model of berlin is going to help him. in hot weather the german

capital is an urban heat island thermal imaging shows how populated urban areas function like contemplate they can be up to 8 degrees warmer than outlying areas. the researcher is using this mini world to find a solution. inside this model of a city apartment and ice cube will demonstrate how much heat gets through. the test houses made of regular building materials. to see what happens when the sun shines on a brick building the building warms up and what happens if we use other materials insulate the facade of or if we put a tree in front of it. using time lapse imaging we can see how people fare in this kind of building it only takes half. an hour for the house

to really heat up very soon they would be practically melting in the heat and no wonder it's over 30 degrees. buildings as we've reproduced them here in the model absolve the heat energy of the sun very well and stoled its energy very well. this is due to the albi to what effect with the color of a building material dictates how much radiation from the sun is reflected by its surfaces. in the case of blank slate for example the albi don't value is 0 point one that means just 10 percent of the rays from the surface are reflected. with red roof tiles the values between 0 point one and 0.35 and with white facades like the ones common in greece the al beat overvalue is between 0.5 in 0.9 the lower the value of their for solids or

roofs the hotter the buildings in the city will be. now the expert tries simple countermeasures 1st external thermal insulation panels . if we want to see what effect this has on the building ultimately insulating the facade not only ensures that heat stays in the apartment it also keeps heat out of the apartment. next comes a coat of light colored paint this reflects the sunlight and so creeps the heat out . brightly painted insulated the house then gets a layer of greenery on its roof before being bathed in another half hour of 1000 watt sunshine a couple of shade providing trees round off the protective measures. when behold this time our hypothermic resident. it's still on its feet no wonder with an

interior temperature of almost $23.00 degrees. since now about $23.00 degrees in the apartment and compared to the temperature of around 30 degrees at the start of our experiment that's a big drop in the wind. which all goes to show that paint can play an important role in easing the city's he problem. as can green spaces in a city. and they don't only offer a fresh mint. it's a paradox while the habitat of wild animals shrinks thanks to expanding cities some creatures are fleeing to urban areas and finding refuge in them. even develop into unique groups of city developing animals.

urban foxes live among us but make only occasional fleeting appearances there are a growing presence in cities and have proven to be highly adaptable. evolutionary biologist sophia q make researchers berman's fox population for wild animals the city is a challenging habitat. you have to pam in mind will sort of a heart attack the city is it's such an artificial environment and there's so much manmade imposed that foxes have to withstand the light and noise traffic i find that fascinating to me to me and. give me has been gathering data on urban foxes for the last 5 years she's equipped 17 of them with a transmitter that allows her to track their movements she's also set up cameras near foxholes in order to monitor the activities of their inhabitants. and women

must also at the moment i'm trying to find out if they're actually hit. i know they're in the area but it's a wide area so there are lots of folks than and i'd like to know which one they're actually use out the moment but let's not. kid is writing a doctoral thesis at the lab rats institute for zoo and wildlife research on the behavioral ecology of red foxes in urban environments. she cited specimens in parks and even in berlin's government district. yet none of the strong smell indicates fox has offered some market. that goes a rabbit. as we can see there are rich pickings for foxes here. he's also. one of the fox so sophia kimock has located is beneath containers at the edge of a park the foxes keep a low profile during the day but they did leave traces of the monkey know him if

you look closely you can see a footprint up here to you. urban foxes live in close proximity to the human population how come given that they're naturally shy animals now they haven't well they found a habitat in the city where no one is preying upon them as is the case in the countryside whether many food sources her own of all those. folks is a highly opportunistic and the anything they find although they're especially good at hunting mice and other brighton's they can also live off rotting fruit earthworms and all sorts of things really. there is no shortage of trash in the city it's one big buffet as far as the foxes are concerned. berlin is believed to be home to between 5010000 foxes fox cubs born in the city hard on feast by the hustle and bustle of the big city. foxes are becoming ever less

timid. sophia q. makes research has revealed that berlin has its own indigenous population and the animals are in fact genetically different from their country cousins. the stock kinds of. the city limits seem to mark a barrier between fox populations the still leave men between the city and the country science but it's must if. the forces that live in the city you don't want to leave it to you and says that live in the countryside don't want to venture into the city probably because they're afraid they're not used to being close to humans and. her research has also shown that urban foxes mark out their territory and like to stay in it with some exceptions. then you took the foxes reach maturity and autumn and start to migrate to new territory so they make the white.