As a United Nations agency released new climate projections showing that the world is on track in the next five years to hit or surpass a key limit of the Paris agreement, authors of a new study warned Thursday that increasing carbon dioxide in the atmosphere is nearing a level not seen in 15 million years.For the study, published in the journal Scientific Reports, researchers at the University of Southampton in the United Kingdom examined CO2 levels during the Late Pliocene about three million years ago \u0022to search for modern and near future-like climate states,\u0022 co-author Thomas Chalk explained in a series of tweets.\u0022A striking result we\u0026#039;ve found is that the warmest part of the Pliocene had between 380 and 420 parts per million CO2 in the atmosphere,\u0022 Chalk told the Guardian. \u0022This is similar to today\u0026#039;s value of around 415 parts per million, showing that we are already at levels that in the past were associated with temperature and sea-level significantly higher than today.\u0022When CO2 levels peaked during the Pliocene, temperatures were 3ºC to 4ºC hotter and seas were 65 feet higher, the newspaper reported. Chalk said that \u0022currently, our CO2 levels are rising at about 2.5 ppm per year, meaning that by 2025 we will have exceeded anything seen in the last 3.3 million years.\u0022\u0022We are burning through the Pliocene and heading towards a Miocene-like future,\u0022 warned co-author Gavin Foster, referencing a period from about 23 to 5.3 million years ago. It was during the Miocene, around 15 million years ago, when \u0022our ancestors are thought to have diverged from orangutans and become recognizably hominoid,\u0022 the Guardian noted.https://t.co/3sNdmN8mCzNew study covered by @guardiannews, we look at CO2 levels in the Late Pliocene (~3 million years ago) to search for modern and near future-like climate states. At current rates, CO2 will surpass levels experienced by our sub-Family Homininae in \u0026lt;5 years.— Tom Chalk (@ChalkyOceans) July 9, 2020Reporting on the study elicited concern and calls for action from environmentalists and advocacy groups.\u0022Every kilo of CO2 we emit is one we have to sequester later, provided the food doesn\u0026#039;t run out first,\u0022 tweeted Extinction Rebellion Finland, urging the international community to #ActNow.Nathaniel Stinnett, executive director of the U.S.-based Environmental Voter Project, also responded to the report on Twitter, saying, \u0022Big Oil and Gas are killing us.\u0022A new report released Thursday by the U.N.\u0026#039;s World Meteorological Organization (WMO) about global temperatures likely coming in the next five years provoked similar alarm and demands.\u0022It\u0026#039;s still not too late to avoid the worst effects of the #ClimateEmergency. But governments need to act NOW,\u0022 declared Greenpeace, pushing for a #GreenRecovery from the Covid-19 pandemic.The WMO report projects that the annual global temperature is likely to be at least 1°C warmer than pre-industrial levels in each of the next five years. Although it is \u0022extremely unlikely\u0022 the average temperature for 2020–2024 will be 1.5°C warmer than pre-industrial levels, WMO warned certain periods could hit that temperature.Specifically, there is about a 70% chance that one or more months during those five years will be at least 1.5°C hotter than pre-industrial levels and about a 20% chance that one of the next five years will be at least that warm, according to WMO\u0026#039;s Global Annual to Decadal Climate Update, led by the United Kingdom\u0026#039;s Met Office.Annual mean global temperature likely to be at least 1° C above pre-industrial levels in each of coming 5 years (2020-2024).And 20% chance it will exceed 1.5°C in at least one year, per new climate predictions issued by WMO and led by @metoffice#ParisAgreement #ClimateChange pic.twitter.com/MNO0H6UTAh— World Meteorological Organization (@WMO) July 9, 2020In a statement Thursday, WMO Secretary-General Petteri Taalas also pointed to the coronavirus pandemic—which prompted global lockdowns that briefly caused planet-heating emissions to drop—as an opportunity to pursue bold recovery plans that incorporate policies that combat the climate crisis, such as rapidly transitioning to renewable energy worldwide.\u0022WMO has repeatedly stressed that the industrial and economic slowdown from Covid-19 is not a substitute for sustained and coordinated climate action,\u0022 Taalas said. \u0022Due to the very long lifetime of CO2 in the atmosphere, the impact of the drop in emissions\u0026nbsp;this year is not expected to lead to a reduction of CO2 atmospheric concentrations which are driving global temperature increases.\u0022\u0022Whilst Covid-19 has caused a severe international health and economic crisis, failure to tackle climate change may threaten human well-being, ecosystems, and economies for centuries,\u0022 he continued. \u0022Governments should use the opportunity to embrace climate action as part of recovery program and ensure that we grow back better.\u0022Taalas added that \u0022this study shows—with a high level of scientific skill—the enormous challenge ahead in meeting the Paris agreement\u0026nbsp;on climate change target of keeping a global temperature rise this century well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5°C.\u0022While some scientists and activists have criticized the 2015 Paris climate agreement as not ambitious enough, it is backed by nearly all nations on Earth. U.S. President Donald Trump began the one-year withdrawal process in November 2019 but former Vice President Joe Biden, the presumed Democratic presidential nominee, has vowed to rejoin the accord if he wins this year\u0026#039;s election.