Greta Thunberg isn't easily intimidated.The 17-year-old Swedish activist wasted little time on Tuesday to push back against US President Donald Trump's description of climate campaigners as “the perennial prophets of doom" who predict the "apocalypse.”Though Trump didn't mention her directly in his speech at the World Economic Forum in the Swiss Alpine resort of Davos, it was clear he had his sights on Thunberg, who shot to fame a year ago by staging a regular strike at her school and sparked a global environmental movement. She then beat the US president to receive Time magazine's award as the 2019 Person of the Year.Climate Activist Greta Thunberg Named TIME’s ‘Person of The Year’Thunberg Accuses Political Leaders of Escapism“The facts are clear, but they are still too uncomfortable for you to address,” she told business and political leaders in Davos just after Trump's speech, also without directly mentioning the president.“You just leave it because you think it’s too depressing and people will give up, but people will not give up. You are the ones who are giving up.”16-year-old Climate Activist Greta ThunbergThunberg brushed aside Trump's announcement that the US would join the economic forum's initiative to plant 1 trillion trees across the globe to help capture carbon dioxide from the Earth’s atmosphere.“Planting trees is good of course but it’s nowhere near enough.” 16-year-old Climate Activist Greta Thunberg"It cannot replace mitigation," she added, referring to efforts to drastically cut emissions in the near term.‘Pretty Much Nothing Has Been Done’: Greta Thunberg Rues in DavosVerbal Spate Going on for MonthsThunberg accused leaders of "cheating and fiddling around with numbers" with talk of cutting emissions to 'net zero' – that is, emitting no more carbon than is absorbed by the planet or technical means – by 2050.She and Trump have been sparring for months, but Thunberg did not seek to upstage the US leader by walking out of his speech, which was largely focused on trade and economics instead of the climate issues that the WEF has made a focus of at its meeting this year.Last month, Trump told Thunberg in a tweet to “chill” and to “work on her Anger Management problem."It prompted a dry and humorous response from Thunberg, who then changed her Twitter caption to read: “A teenager working on her anger management problem. Currently chilling and watching a good old-fashioned movie with a friend.”‘Chill, Greta, Chill,’ Says Trump; Teen Gets Back With Sassy ReplyEarth just finished its hottest decade on record with the five last years as the five hottest years on record, according to the US and other science agencies. Scientists repeatedly point to more extreme weather as a problem worsened by human-caused climate change.There have been 44 weather and climate disasters in the United States that caused at least $1 billion in damage since 2017, killing 3,569 people, according to the National Oceanic and Atmospheric Administration.Thunberg is not the only young activist to highlight the climate emergency, and was joined on a keynote panel by three others, all of whom said politicians and executives are not doing enough.A survey of CEOs released this week by financial firm PwC showed that executives rank climate issues as only the 11th most serious risk to their businesses' growth.Brazilian Prez Bolsonaro Calls Activist Greta Thunberg a “Brat”Aware Teenagers Across the World Are Leading the Campaign Against Climate ChangeNatasha Wang Mwansa, an 18-year-old from Zambia who campaigns for girls’ and women’s rights, said “the older generation has a lot of experience, but we have ideas, we have energy, and we have solutions."And Salvador Gómez-Colón, who raised funds and awareness after Hurricane María devastated his native Puerto Rico in 2017, said young activists are doing more than just talking.“We’re not waiting five, 10, 20 years to take the action we want to see. We’re not the future of the world, we’re the present, we’re acting now. We’re not waiting any longer.”16-year-old Climate Activist Greta ThunbergThunberg cited a report released in 2018 by the UN's science panel that calculated the amount of additional carbon dioxide the atmosphere can absorb before global average temperature increases exceed 1.5 degrees Celsius (2.7 Fahrenheit). Leaders agreed to try to stay below that threshold when they signed the 2015 Paris climate accord, but scientists warn the chances of doing so are dwindling.Greta Thunberg accuses world leaders of 'creative PR'Massive Reduction in Emission Required Over the Next Two DecadesThunberg noted that the remaining carbon “budget” to confidently meet that target stood at just 420 gigatons of CO2 two years ago, the equivalent of 10 years of global emissions. Even with a more optimistic calculation, keeping the global temperature rise below 1.5 C would require a massive reduction in emissions over the next two decades.While there has been widespread criticism both inside and outside the United States over Trump's decision to pull the US out of the 2015 Paris climate accord, Thunberg said the rest of the world, too, was effectively missing the targets set down in that agreement."My generation will not give up without a fight," Thunberg said.UK broadcaster calls Greta Thunberg 'mad, dangerous' We'll get through this! Meanwhile, here's all you need to know about the Coronavirus outbreak to keep yourself safe, informed, and updated. The Quint is now available on Telegram & WhatsApp too, Click here to join.