The planet on which we all live is a dynamic and ever-shifting ecosystem. But there have been disturbing trends in recent decades that our global climate is beginning to undergo a dramatic shift. The politics of man-made climate change continue to play out in the United States (and in other nations to a lesser extent), but the science suggesting that the planet is warming is nearly unanimous. Regardless of the cause, global climate change is happening. This week’s publication by the United Nations about the likely effects of climate change highlights the very serious problems that are could occur. This week, we’ll take a closer look at these potential impacts and how they might affect the United States in particular.

The biggest and most obvious impact of global climate change (and a warming planet in general) is rising sea levels. As the temperature warms, glaciers and ice caps become less stable and begin to melt. Most projections for sea level rise predict a likely increase of around half a foot to six and a half feet by the year 2100. Even a modest increase to this extent could directly impact hundreds of millions of people. This includes at least five million Americans whose homes would be completely underwater. After the year 2100, the predictions become more varied, but also potentially more dire. In the most extreme scenarios where the majority of polar ice melts, sea levels could rise by dozens of feet. This would mean entire countries like Bangladesh or the Netherlands would be submerged.

To be fair, the science on these worst-case scenarios is by no means complete and such drastic sea level rise would likely occur over the span of a couple hundred years. However, there are other scenarios that are far more likely and more immediate. Some sea level rise is nearly certain, which brings with it large-scale population migrations and refugee crises. The world has already seen the humanitarian and political problems that arise out of warfare-driven refugee migrations, and there is no reason to doubt that these problems would worsen for climate-driven migrations. Making matters worse is the fact that wealthier and more developed nations will be impacted by this as well, meaning they will have fewer resources with which to solve the problems of refugee migrations.

But sea level rise isn’t the only meteorological problem caused by climate change. Severe weather is likely to become more intense, hurricanes are stronger due to the presence of warmer waters, and dry climates (such as those found throughout the Middle East) can become even drier. With a warmer, drier climate we are more likely to see conflicts over water resources increase in the coming decades. Though advances in desalination could help stave off the worst of these effects in coastal areas, landlocked parts of South America, Africa, Central Asia, and the Middle East can see much more instability. Here again wealthier nations will have a more difficult time supporting developing nations and maintaining stability. From an economic perspective, the U.N. report estimates that most advanced nations would suffer at least a 1.2 percent loss in GDP from the anticipated two degree rise in global temperature.

These negative impacts also create national security opportunities for other nations. A decrease in polar ice means that more land and sea lanes will open up around the north pole. Russia and China in particular are in a mad rush to control newly opening sea lanes along the Arctic Ocean. Russia, which has historically always sought a warm water port, will have much more access to ports along its northern shore. China, for its part, can cut the shipping time to markets in Europe by days or even weeks. Canada and Alaska will also benefit from open waterways along their northern shores. If America and Canada cannot capitalize on these new shipping lanes, it will mean a substantial disadvantage for North American businesses and commerce. This could shut out America’s main shipping partners from these markets, leading to higher prices and decreased access to goods for the average American.

Fortunately, climate change is a gradual process. Though time appears to be running out to prevent some of the more impactful changes, most climate scientists believe we are already passing a point of no return on climate change. Still, even under the most dire projections, nations have years or even decades to prepare low lying areas and at risk populations. This is somewhat more manageable for wealthy, developed nations to accommodate. But others (like Bangladesh) will have a much harder time coping with the economic, social, and infrastructural problems of climate change. Here, the United States can step up to assist these nations. Not only does this promote America’s image on the world stage, but it also helps prevent more direct problems later on like civil unrest or population migrations. It’s in everybody’s interest to start solving this issue. Regardless of how or why this is happening, it’s time to begin preparing for the worst before it’s too late.