I’ll never forget hearing the news of the tsunami that struck in the Indian Ocean 10 years ago. The images were gut-wrenching: entire towns razed from Indonesia to Somalia; raging waters sweeping away people’s homes; hundreds of thousands killed and many more separated from their families.

Today of all days, we pause to remember those we lost—from farmers and fishers to travelers from our own lands. I know that there are no words to express such a horrific loss. There’s no way to wipe away the pain of parents who lost a child, or children who lost their parents and were forced to assume adult responsibilities at a tender age.

We recognize the millions of people who contributed to the recovery effort. And we honor those who have continued to work in the years since to help the victims pick up the pieces and rebuild their communities. The tsunami was one of the worst we have ever seen, but it brought out the best in all of us.

It also sounded a warning. We know that many regions are already suffering historic floods and rising sea levels. And scientists have been saying for years that climate change could mean more frequent and disastrous storms, unless we stop and reverse course. Last year I visited the Philippines and saw the devastation of Typhoon Haiyan. It is incomprehensible that that kind of storm – or worse – could become the norm. The time to act on climate change is now – before it’s too late to heed the warning.

On this day of reflection, we mourn with our friends in Asia and Africa who were affected by this terrible disaster. We commit to the hard work still ahead to help the region build safer, more resilient communities. And we pledge our best efforts to leave our children and grandchildren a safer and more sustainable planet. Future generations are counting on us.