Last week Bill Gates published 17-page memo On their personal website, critics said they were pitting climate and public health efforts against each other when they should instead be working in tandem.
On Monday night, speaking at the California Institute of Technology in Pasadena, Gates redoubled his efforts, brushing aside criticism from across the ideological spectrum, including climate scientists and President Trump.
Stressing that philanthropic resources are limited, Gates said he has shifted some of his efforts from preventing climate change to reducing human disease and malnutrition in a world that he said will undoubtedly become warmer.
UN Emissions Gap Report 2025The report, published on Tuesday, said it is likely that by 2100 global temperatures will rise by 2.0 to 2.4 degrees Celsius above pre-industrial levels. Gates said he believes the figure will be closer to 3 degrees Celsius.
“Real action is everything we do to help the most vulnerable people on the planet,” he said. He went on to say that he wants to refocus on scientific innovations that will remove the costs of climate change – what he called the “green premium” – from technologies to fight hunger and disease in the world's poorest countries.
Climate scientists have raised concerns about Gates' memo released last week, arguing that it inaccurately separates the problems of disease and hunger from climate change. “These are not isolated problems, these are problems that are exacerbated by this very problem,” said Katherine Hayhoe, a leading atmospheric scientist studying climate change, at a forum Tuesday afternoon with other scientists.
At the California Institute of Technology, in front of more than 1,000 people – mostly students and professors – Gates expressed frustration with climate scientists who criticized his memo as wrongly downplaying the potential impacts of climate change.
“What world do they live in?” he asked at one point, arguing that his critics don't take into account the fact that you can do more to save lives by spending money to fight disease and other problems than by investing in cutting carbon emissions.
“It's a numbers game in a world with very limited resources,” Gates said Monday night. “More limited than they need to be.”
Gates also rebuked Trump, who he said “completely misinterpreted” the memo in his report. True Social Post last Wednesday it suggested that Gates no longer believes in climate change.
“I'm a climate activist, but I'm also a child survival activist, and I hope you are too,” Gates told the crowd at Caltech. “This is the best way to ensure that everyone has the chance to live a healthy life, no matter where they were born or in what climate.”
The billionaire said his shift in focus to human health is aimed at supporting poor countries that typically receive aid from the United States and other rich countries, while the United States has rejected such largesse. Trump administration in July stopped most of all foreign aid payments, which account for only about 1% of national budgets but which researchers at the nonprofit Center for Global Development have found save about 3.3 million lives worldwide.
At Caltech, Gates also discussed technologies he supports to mitigate climate change, including fusion reactors and geoengineering.
Gates' critics in the climate science world say he's focusing on the wrong things. “He kind of continually downplays the importance of the clean energy transition using the technologies we have in favor of promoting some future technologies,” said Michael E. Mann, a climate scientist at the University of Pennsylvania. Some of these technologies could take decades to implement at scale, Mann said. “We don’t have decades to deal with the climate crisis.”
