Weightlifter David Katoatau made headlines in 2016 with his joyful dance at the Rio Olympics.  After dropping his weights, he spun and waved his arms, a gleeful look of triumph on his face as the audience cheered.

But Katoatau was not celebrating his sixth-place finish. His home island, Kiribati, is in danger of becoming completely submerged by rising sea levels, and his dancing was his way to raise awareness. In an open letter he wrote, “The simple truth is that we do not have the resources to save ourselves. We will be the first to go. It will be the extinction of a race. Open your eyes and look to the other low-lying level islands around the Pacific — they will soon fall with us.

“In the not too distant future, we will all drown.”

Indeed, the small Pacific island is in danger of becoming completely submerged in as little as 30 years. The residents already suffer droughts and flooding that threaten the island’s fresh water supply.

Reporter Karl Mathiesen reported in the Guardian, “The island’s drinking water is in perpetual crisis. Groundwater wells are polluted and increasingly salinized by rising seawater. Treated government water reaches some communities, but only runs for a few hours each week.”

Small, low-income island nations like Kiribati present a warning to the rest of the world for the devastation that rising sea levels and droughts will bring to human civilizations. The science is clear and its results are damning.

The world will enter what social critic James Howard Kunstler calls “the long emergency,” a state of exacerbated and constant scarcity which will threaten, if not destroy, the stability of society.

The UN, the EU, the G7 and an increasing number of states have classified climate change as a threat to global and national security. A government-commissioned report by the German thinktank Adelphi examined how environmental changes caused by climate change.

“Terrorist groups are increasingly using natural resources – such as water – as a weapon of war, controlling access to it, and further compounding, and exacerbating resource scarcities,” Lukas Rüttinger writes in the report titled “Insurgency, Terrorism and Organized Crime in a Warming World.”

Climate change causes droughts, which leads to shortages of essential crops, water and foodstuffs, the commodities needed to survive. When these commodities run out, citizens turn to radical terrorist groups rather than their bankrupted states for protection.

In the Lake Chad region, for example, the terrorist group Boko Haram has capitalized on the desperation-caused by extreme poverty, and drought exacerbated by global warming to recruit new soldiers. A high population growth rate of three percent further strains resources. Lake Chad has traditionally been a source of freshwater and irrigation for farming, but over the past 50 years, a combination of increasing use and changing climate has caused the lake to shrink by 90 percent.

Because many disease-carrying insects such as mosquitoes, need warm temperatures to reproduce, global warming exacerbates the spread of infectious diseases, creating a dangerous feedback loop of social instability and epidemics. The disease has spread into highland regions of East Africa where it did not previously exist. Cholera, a disease spread through contaminated water and food, was wiped out in most of the developed world but is now seeing a reemergence.

Ironically, as the consequences of climate change become more apparent, the political response has grown weaker. In January 2007, Former President George W. Bush addressed Congress saying, “America’s on the verge of technological breakthroughs that will enable us to live our lives less dependent on oil. And these technologies will help us be better stewards of the environment. And they will help us to confront the serious challenge of global climate change.”

Special interest groups, particularly the oil lobby, have launched an extensive campaign to portray climate change as uncertain and the green energy initiative as wasteful and corrupt. Today, the Republican Party outright denies climate change. Former President Richard Nixon created the EPA. Trump has been disassembling it.

Reasonable people can view evidence and come to different conclusions. It is not reasonable to knowingly and willingly disregard evidence altogether. It is high time for U.S. leaders to recognize that climate change is not only an environmental disaster but also a national security threat, and commit to policy which treats it as such.