For the third day in a row the unofficial record for the global average temperature has been set

Even though the dataset used for the unofficial record goes back only to 1979, Dr Kapnick said that given other data, the world is likely seeing the hottest day in "several hundred years that we've experienced."

Scientists generally use much longer measurements — months, years, decades — to track the Earth's warming. But the daily highs are an indication that climate change is reaching uncharted territory.