Researchers say by the end of this century, parts of Australia could see dangerous heat most days of the year. 

A new study by Harvard University scientists has forecast the effect of varying global heat levels to the year 2100. 

Their study suggests that the tropics, including northern parts of Australia, are likely to see temperatures of over 39℃ on more than 150 days per year. 

The more southern parts of Australia are predicted to have deadly heatwaves every year. 

The findings suggest that CO2 emissions from human activity could drive global increases in exposure to extreme temperatures in the coming decades, even if global warming is limited to 2℃, in accordance with the Paris Agreement.

A series of deadly heatwaves have impacted major cities in the past decade. The effects of climate change on heatwaves threaten the habitability of large areas of Earth’s land surface if greenhouse gas emissions are not curtailed. 

Very high temperatures pose a threat to public health, with extreme heat contributing to heat cramps, heat exhaustion, and chronic illnesses.

To predict global mean changes in temperature, CO2 concentrations, and relative humidity, Harvard researchers analysed predictions from global climate models, human population projections, and the relationship between economic growth and carbon emissions. 

They estimated that there is only a 0.1 per cent chance of limiting global average warming to 1.5℃ by 2100, in line with the updated Paris Climate Agreement goal. 

Instead, they predicted that the change in global mean temperatures will likely approach 2℃ by 2050. 

They projected that by 2100, many people living in tropical regions - such as India and sub-Saharan Africa - will be exposed to dangerously high heat levels during most days of each typical year. Additionally, deadly heatwaves, which are currently rare in the mid-latitudes, could happen every year in this region - located between the two tropics and the polar circles. For example, the authors predicted a 16-fold increase in the occurrence of dangerous heatwaves in Chicago, USA.

The authors suggest that without adaptation measures there may be large increases in the incidence of heat-related illnesses - particularly in the elderly, outdoor workers, and those with lower incomes - and that more ambitious targets to reduce emissions are needed.

The study is accessible here.