Giant CO2 vacuum（真空） cleaners. Miracle（奇迹） dust in the fields. Algae（[植] 藻类） farms in Africa. High-tech efforts to stop global warming. 10 years from now is too late. We need to start now and research it from all angles.

  What is most effective? What can be implemented later? But which innovations can really mitigate（减轻） the climate crisis? And which ones should be used with caution（ 小心）? We can't take one problem we humans have created and add another on top. I find that very unappealing.

  High-tech innovations are breaking new ground, but can they really stop climate change? Massel Rensmann is doing the rounds in his garden in western Germany's Rein（缰绳） Hesse region. Most of his plants have recovered from last summer's heat wave. The lawn（草地） which was exposed to the sun turned into a field of stubble（残株）. It looked nothing like a lawn anymore. It looked like it was in southern Spain and it hadn't rained for 30 years.

  It was alarming. At one point we just stopped watering it. The drought stress was too much. The consequences of climate change are palpable, both here in the garden and more dramatically elsewhere in the world. Massel Rensmann believes that something has to change, on a small as well as a large scale. There's a wide range of solutions.

  There's no one answer. It's not just down to electromobility or rainwater（雨水） management or giving up meat. There are so many constructive（建设性的） solutions that work（使工作） well. Massel will show us later which of these solutions he's involved in professionally. Intensive（加强的） research into climate change mitigation has been conducted for several years now. In Iceland, nature offers a solution with an ideal combination of ingredients geothermal（地热的） energy, volcanic（ 火山的） rock and plenty of water.

  Like a spaceship stranded（使搁浅） in the middle of nowhere, the Orca Carbon Capture Plant is the first of its kind. Orca uses giant collectors to filter（滤波器） carbon dioxide, a harmful greenhouse gas from the atmosphere. The filter captures the CO2 molecules while releasing the cleaner air back into the atmosphere. Once the filters are full, you close off the compartment（车厢） that the filter（滤波器） is in, and you apply heat to around 100 degrees Celsius, which releases the CO2 that we can then capture and collect. The heat is produced renewably from a geothermal power station. The Orca plant has collected 4,000 tonnes per year so far, the equivalent of the greenhouse gas emissions of 360 people in Germany.

  It's not a lot. I mean, the globe emits around 36 billion tonnes of CO2 per year. But this is a new technology. We went from capturing milligrams（毫克） to kilograms to tonnes to 4,000 tonnes, and so we are on our way to a huge and massive scale-up. More plants will be built soon, not just here in Iceland. Wherever there is volcanic rock, these plants can be built, as the CO2 can be permanently stored in the rock.

  That's what's happening under these igloos（圆顶建筑） nearby. Olahwyrtetur Gunatson explains to us exactly how. The company he works for developed the process. It's simple, at least in principle. So this large pipe that we are looking at is a pipe from the geothermal power plant, injecting（注入） geothermal（地热的） water back into the ground, two kilometres deep, into the geothermal area. And what Carpfix does is to actually borrow that pipe and inject our CO2 charged water, coming through this smaller pipe, into the bigger run, and also going down into the earth, where the CO2 from the water is mineralised in less than two years.

  It's a natural process, but it runs more quickly here and sequesters（使隔绝） large quantities of CO2. It's all a question of the right ratio（比率） between pressure, temperature and depth. What I'm holding（拿住） here in my hands is two cores that show the before and after of the Carpix methods. One of them is the Passaltic rock that you can see has a lot of holes in it. So the water that we inject into the ground goes through these holes and the CO2 in the water dissolves（使溶解） metals in the rock and forms a mineral called calcite（方解石）. And this core that I'm holding here shows you the white dots is CO2 that has been turned into stone, filling up the holes in the rock.

  The CO2 can stay in the rock forever. Several hundred million tonnes of CO2 could be stored under this plant alone, and much more worldwide. In principle, it's a brilliant process, says Tobben Aman. At the University of Hamburg, he's working on ideas to remove CO2 from the atmosphere. But of course, you do have to ask yourself what it costs, and if there are other solutions that can make（使） a contribution which are perhaps less costly（昂贵的）. But direct air-carbon capture is one way.

  There's huge potential. At least in places where there is enough Basalt（玄武岩） rock and green energy. But is it really the way to stop climate change? You cannot use this technology as an excuse for business as usual. It can only be an addition to all of our other efforts in reducing emissions, reducing the dependency on fossil（化石的） fuels, changing over to greener（生手） sources of energy. We need to do all of those things.

  According to the UN Intergovernmental Panel on Climate Change, carbon dioxide emissions need to be reduced quickly and drastically（激烈地） to hold（拿住） global warming to 1.5 degrees Celsius as laid out in the 2015 Paris Climate Agreement. But to ensure this, existing greenhouse gases also have to be removed from the atmosphere. This is known as negative emissions. The curve needs to fall below zero. Currently, just two gigatons of carbon dioxide are extracted（提取） from the atmosphere per year, mainly through reforestation. A tiny fraction is extracted using technical methods.

  According to one study, these would have to extract over 1,300 times more by the middle of the century than they do now. As it is now, it won't work. It has to be done faster. If we facilitate（（不以人作主语的）使容易） more research, of course it will go faster. But it's not all we need. The right political guidelines are also necessary to specify which direction we want to go in, which goals we want to have.

  At home in his garden, Marcel Rensmann also relies on a small-scale technical solution, putting up umbrellas to protect against the heat. We have two umbrellas for the area where children play. At 30 degrees in the shade with direct sunlight, the garden faces south. It's not very sensible to be there without shade. Is the idea of a giant parasol to cool the whole planet a crazy one? Actually not.

  It's been around for some time. In 1991, the Pinatubo volcano erupted in the Philippines. Hundreds of people were killed and the damage was enormous. Yet the volcano did something that researchers all over the world have been studying ever since. The volcano ejected（逐出） sulphur（硫(磺)） gas into the stratosphere（同温层） where it reacted with oxygen to form tiny particles. This formed a thin layer which reflected and blocked the sunlight, creating a kind of giant shield like a parasol for the planet.

  For months, temperatures were half a degree cooler（凉的） than usual. If volcanoes can do it, why can't humans? Special aircraft could bring the sulphur up to the stratosphere.