there were two further challenges the Earth faces when it recovers from Covid-19 - climate change and bioterrorism.In his new book, he explains 'the clear answer' to what people should do collectively over the next decade.He reveals why humans need to cut carbon emissions to zero, and how to respond after the pandemic finally comes to an end in the future.He says 51bn greenhouse gases are added to the atmosphere every year, but the Earth should aim for zero to stop the warming and worst effects from happening.He used the analogy of climate being a bathtub that is slowly filling up with water, even if the flow is slowed down, it still overflows.He admitted the only sensible goal is to reduce emissions to zero.He wrote in The Guardian: "This.