Dangerous heatwaves in Europe could break further records, the UN says.
It is hard to immediately link these events to climate change because weather - and oceans - are so complex.
Studies are under way, but scientists already fear some worst-case scenarios are unfolding.
"I'm not aware of a similar period when all parts of the climate system were in record-breaking or abnormal territory," Thomas Smith, an environmental geographer at London School of Economics, says.
"The Earth is in uncharted territory" now due to global warming from burning fossil fuels, as well as heat from the first El Niño - a warming natural weather system - since 2018, says Imperial College London climate science lecturer Dr Paulo Ceppi.
Here are four climate records broken so far this summer - the hottest day on record, the hottest June on record globally, extreme marine heatwaves, record-low Antarctic sea-ice - and what they tell us.