I hear from many people that they can't quite visualize the worst potential impacts of climate change.

I wonder if living through 2020 will change that. As we've all seen firsthand, that one threat -- an insidious virus -- can mean everything from fatalities spiking in just weeks, to food and grocery shortages, to schools closing, to everyone (well, almost everyone) wearing a mask just to go outside and check their mail.

If we don't act on climate change in this decade, future decades will look and feel a lot like 2020. And one of the most dystopian realities we'd see would be the exponential increase in something we're already seeing in isolated cases: climate migration.

"If we don't act on climate change in this decade, future decades will look and feel a lot like 2020."

Let's demystify the notion of climate migration. It's not some distant reality, or some futuristic alternative world. We have climate migrants -- or refugees -- today. There are people who have left where they were living because droughts became so significant they couldn't grow food, or they lost their water, or there is conflict over their water sources so they have to move in order to find a place to sustain living. There are people who've had to move because of sea level rise, changes in the thawing of the permafrost, and a drying up of community wells.

"Let's demystify the notion of climate migration. It's not some distant reality, or some futuristic alternative world. We have climate migrants -- or refugees -- today."

Now, climate migration hasn't reached its crescendo. The issue has not yet risen to a level causing the international community to act. But, if we don't respond rapidly, the day will come when we'd quickly have millions of climate refugees. It is just a matter of time before the global refugee process has to incorporate the idea of climate migration into an overall planning framework.

What are the implications? They extend well beyond just hunger. Food and water security is global security, period. If people can no longer make a decent living farming, fishing and herding, the way their families have for generations, they will have no choice but to seek other opportunities.They may seek those opportunities in places with economies that don't have the ability to support them. If they migrate to cities -- which is today happening at an unprecedented rate -- they will bring hunger and malnutrition with them.

"It is just a matter of time before the global refugee process has to incorporate the idea of climate migration into our overall framework."

What about the families in the Middle East and North Africa who can't afford to buy food for their children because the prices have skyrocketed and their supermarket shelves are literally empty? They too could become desperate and they then will need to begin looking for alternative means to survive.

It is not a coincidence that immediately prior to the civil war in Syria (from 2006-2011), the country experienced the worst drought on record. As many as 1.5 million people migrated from Syria's farms into Syria's cities, intensifying the political unrest that was beginning to brew. I'm not telling you that the crisis in Syria was caused by climate change. No, obviously it wasn't. It was caused by a brutal dictator who repressed, barrel bombed, starved, tortured, and gassed his own people. But the devastating drought clearly made a bad situation a whole lot worse.

"Climate change will only exacerbate migration in places already enduring economic, political, and social stress."

We have already seen tension rise around the basins of the Nile, Central Asia's Indus River, and the Mekong in Southeast Asia. Areas facing unrest, instability, and weak governance are breeding grounds for violent extremism. Climate change will only exacerbate migration in places already enduring economic, political, and social stress. If people think the current migrations to Europe are a political challenge, wait until even larger portions of the Middle East and Northern Africa knock on Europe's door because citizens can't grow food and live day-to-day in 120-degree heat.

For the last few years, in places like Honduras, climate change has impacted agriculture at certain altitudes. As a result, people are abandoning lifetime-held land becuase of their inability to grow crops, and they are migrating. These new mobile communities are climate refugees.

And then, there is the island nation, Palau, where its President is literally planning where his people will move. This is a nation that will not exist in future centuries because of sea level rise -- and other parts of the world will no longer exist if we don't respond now.

"Climate change is -- to borrow a term from the Department of Defense -- a 'threat multiplier.' Even if it doesn't ignite conflict, it has the ability to fan the flames and make situations much more complicated..."

Climate change is -- to borrow a term from the Department of Defense -- a "threat multiplier." Even if it doesn't ignite conflict, it has the ability to fan the flames and make situations much more complicated for societies, governing systems, and political leaders to deal with.

Climate change can be a complicated issue, but climate migration is not really a complicated equation. It's simple to figure it out. Human beings are like any other species on the planet: when our environments no longer provide us with the things we need to survive, we will do everything we can to find a new place to live.

In fact, over the last few years, Europe endured one of the worst refugee crises in decades, brought on by conflict in the Middle East and North Africa. And unless we all step up to meet the urgency of this moment on climate change, the horrific refugee situation of the last decade will pale in comparison to the mass migrations that intense droughts, sea level rise, and other impacts of climate change are likely to bring about.

"Human beings are like any other species on the planet: when our environments no longer provide us with the things we need to survive, we will do everything we can to find a new place to live."

When we talk about climate change, we're not just talking about harm caused to habitats of butterflies or polar bears -- as some people mock and as serious as those effects may be -- we are talking about impacts on people. We are talking about severe droughts, and of rapid sea level rise -- the impacts cities from unpredictable and uncontrollable extreme weather events. We're talking about the impacts on entire countries and of fundamental shocks to the global agricultural system.

When you factor in all of these impacts, you're able to see we're not just up against some really serious ecological challenges, we also need to prepare ourselves for the potential social and political consequences that will stem from crop failures, water shortages, famine, and outbreaks of epidemic disease. We have to heighten our national security readiness to deal with the possible destruction of vital infrastructure and the mass movement of refugees, particularly in parts of the world that already provide fertile ground for violent extremism and terror. Long story short, climate change is not just about Bambi; it's about all of us in very personal and important ways.

"...unless the world steps up to meet the urgency of this moment on climate change, the horrific refugee situation of the last decade will pale in comparison to the mass migrations that intense droughts, sea level rise, and other impacts ... are likely to bring about."

Climate change exacerbates resource competition, threatens livelihoods, and increases the risk of instability and conflict, especially in places already undergoing economic, political, and social stress. Because the world is so extraordinarily interconnected today -- economically, technologically, militarily, and in every other way imaginable -- instability anywhere can threaten stability everywhere. The kind of strife we're talking about cannot be contained by international borders in the same way Europe's borders could not be contained as refugees poured in from Syria.

Climate change is also what we call a "ring road" issue, meaning that climate change affects all the other threats. It will change disease vectors. It will drive migration. And these changes could, in turn, affect state stability and harm global security as a consequence.

"Because the world is so extraordinarily interconnected today -- economically, technologically, militarily, and in every other way imaginable -- instability anywhere can threaten stability everywhere."

Crop yields are down in more than two dozen countries. By 2050 the Midwestern United States could see agricultural productivity drop the lowest it's been in decades. And this is just a preview of what could come: greater chaos in the production, transfer, and provision of food to hungry people who have become refugees because they can't live where they used to.

That's the bad news.

But here's the good news: this will be the decade where big decisions can be made that will help us avoid worst-case scenarios from becoming nightmare realities.

We've never lived through a year like 2020. But the good news is -- we have the power to avoid living through years far worse. The question is, will we do it in time?

For millions who don't have to become climate refugees, let's do all we can now to ensure the answer is yes.