That human activity is a cause of global warming and changing temperatures is a fact that cannot be debated, but until now, scientists had little clue as to what was the extent of damage due to human intervention. A paper published in Nature, based on model simulations of different climate conditions, shows that humans may be responsible for 50-70% change in climate conditions, leading to melting of ice at the Arctic sea. Although the study absolved humans for air flow changes, 70% of which, it said, is due to natural variability, it pointed that 60% of sea ice decline since 1979 was caused by summer-time changes in atmospheric circulation.

While the study is expected to change how we observe climate change, it will also get us to alter our future predictions. With Arctic ice depleting fast—in January it was 1.26 million square kilometres, which was 8.6% below the 1981–2010 average—global warming would need coordinated action from governments. Policy turns in the US—Republicans have presented a bill in the Congress to do away with the country’s Environmental Protection Agency—will end up harming the environment. With global warming accompanying industrialisation, countries would need a concerted approach to tackle its ill-effects.