Deaths and injuries from climate change are set to more than double in the next 25 years, according to estimates to be published soon.

The World Health Organisation is finalising data forecasting that deaths linked to even a very narrow number of causes most closely connected to shifting weather patterns will reach more than 300,000 a year by 2030.

The number of disease-adjusted life years (Dalys) lost - a measure of injury and earlier death - linked to warming will rise in the period to more than 11m.

The data, set to be submitted to an academic journal for publication over the summer, focus on the impact of temperature change on diarrhoea-related disease, malaria and malnutrition, which will be greatest in the developing world.

The estimates will add to the urgency of the debate over efforts to limit the human impact of global warming, highlighted in recent US discussions over the risks to international security caused by climate-related political disruptions and social unrest.

The statistics follow the release this month of the headline findings of the intergovernmental panel on climate change, representing the consensus views of recent scientific research, which warned that the health status of “millions of people” would be affected.

The new WHO estimates build on research by Tony McMichael at the Australian National University, which calculated that in 2000 there were already 166,000 deaths and 5.5m Dalys caused by warming that had taken place since the 1970s.

Scientists say his estimates and the new forecasts represent a necessary and serious attempt to quantify the impact of climate change on human health, but underestimate the true impact.

They only consider a subset of the more direct impacts on health that can be measured, ignoring the effects of increased air pollution and allergens, and changes in the distribution of diseases brought by mosquitoes and other animals apart from malaria.

The figures do not take into account ill-health as a result of more frequent and intense dust and wind storms, forest fires and malnutrition caused by drought, floods, pests and reduced biodiversity; and the damage to health infrastructure and by population displacement.

They also probably under-estimate the impact of climate change in the developed world, notably extreme weather such as the European heatwave of 2003 and recent hurricanes, which are difficult to predict but caused many thousands of additional deaths.