This year's Siberian heatwaves shows just how serious conditions have become. The Arctic is warming at twice the rate of the rest of the planet. Arctic temperatures are estimated to have risen 2C since 1850 compared with 1C globally.
What impact that will have on the world's weather is less certain.
"Looking at the geological record, we don't think we've had CO2 levels as high for about five million years," said Dr Katharine Hendry of Bristol University. "So we really don't know what to expect into the future. We are," she said, "in uncharted territory".
What worries many scientists is that this new climate era we are entering means many places now experience weather conditions beyond anything local ecosystems - or indeed human communities - have evolved to endure.
The record-breaking heatwave in Siberia would have been almost impossible without human-caused climate change, a study has found. The Russian region's temperatures were more than 5C above average between January and June of this year. Temperatures exceeded 38C in the Russian town of Verkhoyansk on 20 June, the highest temperature ever recorded north of the Arctic circle. Such an event "almost impossible" had the world not been warmed by greenhouse gas emissions, they conclude in the study. The current Siberian heat "has contributed to raising the world's average temperature to the second hottest on record for the period January to May". The storms and floods in February this year and ones back in 2015 as other possible examples of Arctic-linked changes .Four of the six main systems that determine this country's weather are driven by conditions in the Arctic. "The link between the Arctic and UK weather is through the jet stream," said Prof Stott, referring to the ribbon of fast-moving air high up in the atmosphere. The jet stream helps move weather systems around the globe. But sometimes it creates "blocking" patterns that can cause weather systems to stall. The unusually sunny spring experienced in the UK this year was caused by a blocking pattern that allowed high pressure systems to dominate the UK for months on end. The so-called "Beast from the East", involves Arctic air blasting the country, driving temperatures below 0C for several days. Over half a metre of snow fell in some areas. The 2018 storm is reckoned to have caused over £1bn of damage and claimed 10 lives.
The extreme temperatures led to a cascade of natural and human disasters. A vast fuel spill was caused by the collapse of a reservoir containing 20,000 tonnes of diesel near the Russian city of Norilsk in late May. Arctic wildfires are estimated to have led to the release of 56 megatonnes of CO2 in June.
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