"Today, no nation can find lasting security without addressing the climate crisis. We face all kinds of threats in our line of work, but few of them truly deserve to be called existential. The climate crisis does," he said, adding that "climate change is making the world more unsafe and we need to act."
The climate crisis is a profoundly destabilizing force for the world, Austin said. As the Arctic ice melts, competition for resources and influence in the region increases. Closer to the equator, rising temperatures and more frequent and intense extreme weather events in Africa and Central America threaten millions with drought, hunger and displacement.
As families risk their lives in search of safety and security, mass migration leaves them vulnerable to exploitation and radicalization, all of which undermine stability, he said. And in the far reaches of the Pacific, rising sea levels and more frequent and intense storms put individuals, families and whole communities at risk, while pushing the limits of the world's collective capacity to respond.
The Defense Department has been impacted directly in just the past few years by extreme weather caused by climate change, he said, providing some examples:
The department has been called repeatedly to support communities throughout the United States and abroad, as they attempt to recover from severe weather events, Austin said.
"From coast to coast and across the world, the climate crisis has caused substantial damage and put people in danger, making it more difficult for us to carry out our mission of defending the United States and our allies," he said.
That's why President Joe Biden has tasked the United States' 18 intelligence agencies with producing a National Intelligence Estimate on the security implications of climate change, he said.
"We in the Department of Defense are committed to doing our part, from increasing the energy efficiency of our platforms and installations, to deploying clean distributed generation and energy storage, to electrifying our own vehicle fleets," he said, adding that "we're not alone," meaning allies and partners are also addressing the threat.
The Climate Change and Sustainability Strategic Approach recently issued by the United Kingdom raises the bar on how militaries can adapt to an operational environment that considers the effects of climate change while advancing military capabilities and resilience, he said.
"The benefits of action extend well beyond the climate, and include opportunities to improve our own operations. For example, when we operate more sustainably, we become more logistically agile and ready to respond to crises," he said.
"We also have a once-in-a-generation opportunity to build an entire economic sector and the global infrastructure for clean energy. The truth is that our shared commitment will allow us to create a safer, more resilient, secure and sustainable future," he said.
"None of us can tackle this problem alone. We share this planet, and shared threats demand shared solutions. I look forward to working with all of you on this vital mission," he concluded.