Dust Bowl drought
The Dust Bowl of the 1930's gives a rough idea of what much of
the globe faces in the coming decades on our current path, except
this drought will be much hotter and drier, and it won't end.

Hell and High Water: The Future that Doesn't Have to Happen

“It may seem impossible to imagine that a technologically advanced society could choose, in essence, to destroy itself, but that is what we are now in the process of doing.”     -Elizabeth Kolbert

What if we ignore the warnings from climate scientists? What if humanity continues a "business-as-usual" emissions path? The news media have catastrophically failed to communicate clearly to the public and politicians what climate science is telling us: unless we change direction quickly, our kids are headed for a world of multiple, irreversible catastrophes. Here's a quick survey of what the latest science predicts we can expect if we stay on our present path. .

A Very Different World

The first thing to wrap your head around is just how drastically we're likely to transform our planet. Recent studies project that by the end of this century, combining our current emissions pathway with likely climate feedbacks, the resulting greenhouse effect will increase the planet's average temperature by four to seven degrees Celsius, with a mid-range of about five degrees temperature increase. That's roughly ten times as much climate change as we've had so far.

When the planet was five degrees Celsius colder: Half of North
America was covered by ice, and sea levels were 300 feet
lower than today.

How big is five degrees Celsius? Twenty thousand years ago the Earth was about five degrees Celsius colder than it's been during historical times, and our planet was a different world. We call it the Ice Age. Florida had the climate and vegetation that you can find now in southern Canada. Giant continental ice sheets a mile thick covered half of North America to as far south as what's now New York City, as well as covering large portions of Northern Europe and Asia. Because so much water was tied up in those massive ice sheets, sea level was 300 feet lower, exposing plains of dry land that are now underwater.

The obvious question is: if planet Earth at five degrees Celsius colder than we're used to means New York City is buried under a mile of ice and Florida has the climate of Canada, what does the planet look like at five or more degrees Celsius warmer than we're used to? We are headed for a world that's very different from the one we know.

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Agriculture In An Age of Drought

The most grave threat for humanity, one that gets little discussion, is likely to be climate change's impact on food production. Drought, extremely high average and extreme temperatures, and irregular rainfall threaten to turn a world of abundance into a world of scarcity.

The heating of the planet will set in motion several processes that combine to bring about a massive expansion of areas too dry to raise food. One of these is desertification: as the global climate warms, the desert belts will expand into areas which are now well-watered, reducing rainfall.

But also, as every gardener knows, higher temperatures mean water evaporates more quickly from soil and vegetation, creating drought conditions even at rainfall levels that would be adequate at lower temperatures. The resulting effect on world agriculture has been termed "Dust Bowlification", for its resemblance to the drought that struck parts of the U.S. in the 1930's -- except this drought will be much hotter, drier, and more widespread. And the new drought, once it starts, won't end anytime soon.

Right now, according to one widely used measure of drought, the amount of land subject to "severe" drought is one percent of the world's land area. In a world warmed by four degree Celsius (which we could reach shortly after mid-century), that's predicted to increase to an eye-popping thirty percent of the world's land surface in severe drought.

Drought resulting from climate change
World-wide drought forecast (measured by the Palmer Drought Severity Index) under a moderate emissions scenario.
During the Dust Bowl the PDSI in the Great Plains briefly dipped to -6, but otherwise rarely went below -3 for the decade

This figure, from a 2010 study by the National Center for Atmospheric Research, depicts a cataclysmic future for humanity, in which many of the world's breadbaskets, as well as most of the areas where large human populations live, are subject to ongoing, searing drought, as bad as or worse than the Dust Bowl. As one commentator described the impacts, “Unlike most earlier droughts over the past millennium, these super-droughts will hit a planet with a population approaching 10 billion -- and they will hit multiple areas simultaneously, making it exceedingly difficult for countries to receive significant outside aid or for large populations to migrate.” We are currently on a higher emissions path than the one modeled in this study, and so we're likely headed for this level of global drought even earlier than the 2060's.

And that diagram might even understate the drought problem. One thing that's not widely appreciated about climate change is that as the planet warms, rain will tend to fall in less frequent, stronger downpours. Even the well-watered areas will tend to whipsaw between drought and deluge. At higher temperatures, plants need water to be more regular, but they'll get exactly the opposite.

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Heat And Its Effects On Food Production

Drought and heat crop failure
Drought and heat have similar results: drastic reductions
in crop yield.

Heat will cause its own set of problems for agriculture, on top of the hardships caused by drought. High temperatures are extremely stressful to crop plants and livestock, drastically reducing yield. Temperatures of 100 degrees Fahrenheit, with 80 percent humidity, are lethal to cattle. Heat waves are especially critical at particular stages of crop development, especially in pollen development stages for grain crops. On our present course, roasting heat waves will be a fact of life, because on a warming planet, temperature extremes rise faster than temperature averages.

Even without heat waves, increasing average temperatures present an enormous challenge for trying to keep the world fed on the emissions path humanity is currently on. One study found that by the time the world hits three degrees of warming (Celsius), average growing season temperatures in the temperate zones will be as high as the most extreme heat waves of the early twenty-first century.
Heat tolerant tropical crop cassava
Farmers in the least drought-stricken areas
of the temperate zones will stave off starvation
for a while by switching to heat-tolerant tropical
crops like cassava. Tropical farmers will not
have that option.
        (Image by David Monniaux via Wikimedia)
In the tropics and subtropics, average growing season temperatures will exceed the most extreme early-21st century heat waves. That's at three degrees of warming. On our present emissions path, we could reach that by mid century, and twice that by century's end.

How will farmers cope with that? Farmers in the least drought-plagued areas of the temperate zones might be able to produce at least some food by switching to heat-tolerant crops native to the tropics, like cassava and sorghum. But half of humanity lives in the tropics and subtropics, which are already the warmest part of the planet -- there is no warmer climate zone to borrow crops from. As temperatures move beyond the tolerance of those tropical crops, there will be nothing else to plant.

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Hot, Acidic Oceans

Jelly fish thriving in anoxic Black Sea
Legacy to our grandchildren? The oxygen-depleted waters of the
Black Sea offer a warning of what the rest of the world's oceans might
look like in coming decades on our current path: a sea full of jellyfish.

Climate change poses a number of threats for the oceans. One is simply that much of the oceans today are adapted to cool temperatures, so warmer water causes these cold-adapted marine ecosystems to be increasingly stressed. But also, heating the oceans causes oxygen depletion: warm water holds less oxygen than cold water, so as the ocean temperatures rise, dissolved oxygen levels drop. The result is predicted to be vast marine dead zones, which would last for a long, long time. One study concluded that "substantial reductions in fossil-fuel use over the next few generations are needed if extensive ocean oxygen depletion for thousands of years is to be avoided."

The other problem is that the oceans are absorbing CO2 from the air, which is making ocean water more acidic. Water needs to be alkaline in order for organisms to make shells out of calcium carbonate, so acidification threatens any ocean life that makes a shell. That means not only clams, oysters, mussels, crabs, and lobsters, but also much of the plankton that make up the base of the ocean food chain, which ultimately are food for for whales and dolphins, and also for the fish we eat.

Add in the effects of the widespread overfishing and poor fisheries management, and the oceans may be headed for widespread marine ecosystem disruption, meaning that future generations won't be able to depend on the harvest of the seas for food, which right now a billion people depend on for protein. There is a class of creatures that is likely to thrive on all of these changes, and they are already on the upswing -- we are on the path to creating an ocean full of jellyfish.

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Rising Seas

The danger of sea level rise is that once the ice sheets really start melting, they are likely to continue melting and raising sea levels for a very long time. We will not have stable coastlines.

City flooding sea level rise storm
The New Orleans scenario is likely to play itself out over and
over: a coastal city protects itself from the rising seas
with levies, until a storm breaches the defenses.

The latest forecasts call for a foot of sea level rise by 2050, and up to six feet by 2100. After that, the oceans would rise relentlessly at six to twelve inches per decade, perhaps more, until all the ice has melted. Much of the global infrastructure, our cities and ports, are built around that interface between land and sea. It's not at all clear how society could deal with a constantly advancing ocean, even if we weren't dealing with all the other catastrophes our present path is taking us towards.

Hurricane Katrina in New Orleans created a scenario that is likely to play out over and over again, all over the world. Cities will try to protect themselves from rising seas with damns and levies. This will work for a while, until the steadily rising seas reach a point that a massive storm can breach the levies, flooding the city. Eventually, the futility of trying to protect coastal cities will be obvious, and they will be abandoned to the rising seas.

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Lethal Heat Stress

On top of all the impacts on our food and water supply, will be the direct impacts on humans physically. High temperatures can kill. Even with the small amount of warming the planet has experienced so far, we are already experiencing episodes of deadly heat. The 2003 heat wave in Europe killed 70,000 people, the Russian heat wave of 2010 killed 55,000.

Both of these deadly heat waves had temperatures at their peak reaching about 104 degrees Fahrenheit. That's a mild preview of what the future has in store for us if we stay on our present emissions path. One study forecasts extreme temperatures up to 120-plus Fahrenheit in much of the tropics, and in the hundred-and-teens for much of the United States, and that was for a global temperature increase of 3.5 degrees Celsius. We could see that much temperature rise by mid century, and twice that by century's end.

Heat index heat humidity danger zone
We're heading deep into the orange zone of the heat index chart, towards
combinations of heat and humidity beyond anything that now exists on our planet.

The Earth's climate as we've known it has a built-in safety feature for humans. Regions prone to extreme high temperatures tend to have low humidity, and areas with high humidity don't get as hot as the dry areas. On our present path, we're going to lose that safety -- heat waves will increasingly combine sweltering humidity with extreme high temperatures, creating heat indexes higher than anyone now alive has experienced.

The limit of human tolerance is a heat/humidity combination so extreme the human body simply cannot rid itself of heat, "even if you're standing naked in front of a fan, sopping wet," in the words of one scientist. It's predicted some areas will start to experience these lethal conditions by the time we get to seven degrees Celsius average global temperature increase. In a high emissions scenario with high levels of feedbacks activated, that could happen by the end of this century. Once we get to a global temperature increase of fourteen degrees Celsius, most of the now-inhabited world becomes subject to lethal heat/humidity combinations. That probably won't happen this century, but we could get there in the 22nd century.

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How will our kids and grandkids react?

How will our children and grandchildren react to collapsing supplies of food and drinking water, and large areas becoming uninhabitable due to heat and drought and rising seas? It's hard to predict the social consequences, but some things are not hard to forecast. The predictable result of massive, global crop failure is that humanity will get brutally reacquainted with its old nemesis, famine. It is likely that a large percentage of the global population will simply starve to death, on a scale dwarfing anything the world has ever seen.

It's likely that hundreds of millions, and perhaps billions, will be on the move as refugees. Throughout human history, competition for scarce resources has been the source of brutal wars, and with multiple climate-related plagues assaulting humanity, the twenty first century is unlikely to be an exception. With thousands of nuclear weapons in the world, it's quite possible that some of those will be used in anger. It's an open question how much governmental or societal structure is likely to be preserved under these conditions.

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Time To Change Direction!

This is not science fiction, or a fringe doomsday scenario. This is the work of the world's top experts, based on mountains of evidence from many different sources. This is real. Because of climate lags and feedback effects, once these effects are well underway, it will probably be too late to stop them from continuing for a very, very long time. The inertia of the climate system means most of these effects would be irreversible for at least a thousand years, even if emissions were stopped once it becomes obvious something is going very wrong with the climate.

This is where we are headed on our current path of greenhouse gas emissions. As they saying goes, if you do not change direction, you are likely to arrive where you are headed. Continuing the path we're on is beyond immoral. We need to make sure everyone understands the implications for their children and grandchildren, make sure young people understand the implications for their own future.

It is critical that we spread the word and demand from our politicians that the time to switch the global economy onto 100% emissions-free energy sources is NOW, as fast as we humanly can.

Next: Your personal action plan for how YOU can help preserve a safe climate for our kids.

Many thanks to Dr. Joseph Romm, editor of the outstanding Climate Progress blog and author of the book "Hell And High Water", for compiling much of the science referenced in this article, especially in this blog posting.