We have all heard of climate change. In fact, many people are tired of hearing about it. Despite all the talk, the most important aspect of climate change has not been made clear: how serious it will be for human being

The news notes facts about the physical world: the ice sheets in Antarctica are melting, seas are rising, coral reefs are jeopardized, 2012 was the hottest year ever in the United States. But we don’t live in Antarctica, a sea rise of a few feet seems like nothing to panic about, most of us have never even seen a coral reef, and 2012 did not feel like the end of the world.

To know how to respond to climate change, we have to confront how those changes will affect people. It is only if we understand how our lives and our way of life are threatened by climate change that we will demand action from our leaders.

You can measure casualties of war, but how do you measure the human cost of climate change?

There is no way to predict the precise number of people who will be harmed by climate change, but it does not take a crystal ball to appreciate that the toll will be staggering.

For example, we know that roughly half the people on the planet live in the watersheds of rivers fed by mountain glaciers. These glaciers store water during the rainy season and release it as runoff in the dry season. As glaciers continue to disappear, one out of every two people on the planet will be directly affected and many of them will suffer severe water crises. I am one such person—my home state of California relies on the Sierra snowpack (not technically a glacier but also melting away) for much of its water and will face unprecedented droughts in the coming decades. Count the human cost of melting glaciers as in the billions.

India and Pakistan will face a crisis as the glaciers that feed the Indus River shrink and disappear. Without enough water from the Indus, which flows first through India, Pakistan may be unable to exist. The Pakistani media speaks openly about the need to threaten nuclear war if that is what it takes to ensure that India allows enough water to flow into Pakistan. Many other examples of climate change making dangerous situations worse can be found. Count this as a human cost in (at least) the many millions.

Droughts will be more frequent and more severe. The Mississippi River transports 60 percent of all American grain exports. It carries enough goods in a year to fill literally millions of semi trucks. Yet last year it was almost shut down because the water level had fallen too much. Even a brief shutdown would have cost billions of dollars and thousands of jobs. A long-term shutdown would have devastating economic consequences. Multiply the impact on this one river by the countless others that will be affected.

As glaciers continue to disappear, one out of every two people on the planet will be directly affected.

A full list of human costs would be very long, so let me just give one more example. As salt water pushes in on fields, as rivers dry up in some places and floods ruin crops in others, the world will see a sharp reduction in agricultural production and a spike in food prices. Every one of us will have to pay more for food. The world’s poorest will simply not be able to afford food and will face widespread starvation and famine. Count this as tens or perhaps hundreds of millions killed and every human on the planet harmed.

What’s the most pressing thing we need to do?

Climate change is a complex problem, but the required solution is clear. We need to raise the price of emitting greenhouse gases. The best way to do so is through a tax on carbon (and other greenhouse gases). The right tax would ensure that people pay the full cost of the carbon they use, including the harm it causes when it goes into the atmosphere. This will encourage people to use less and will support the development and use of renewable energy.

The U.S. cannot do it alone, however, so a domestic carbon tax should be accompanied by a border tax to be paid by any imports that have not paid a comparable carbon tax in their country of origin. Beyond this, we must use the influence and international power of the U.S. to persuade others—especially China—to join us in the effort to reduce emissions and avoid at least the most serious of the costs climate change threatens to impose on us.

If America remains on the sidelines, the problem will not be solved, and the costs will be terrible. (The Daily Beast, May 17, 2013

Not everybody agrees. There has long been a political debate on the subject of climate change, even though the scientific debate has been settled for years. In recent months, perhaps in response to Hurricane Sandy, the national drought of 2012, and the fact that 2012 was the hottest year in the history of the United States, there seems to have been a shift in the political winds.

Oblique view of Grinnell Glacier taken from the summit of Mount Gould, Glacier National Park in 1938. The glacier has since largely receded. In addition to glacier melt, rising temperatures will lead to unprecedented pressures on our agricultural systems and social infrastructure, writes Andrew T. Guzman. Image by T.J. Hileman, courtesy of Glacier National Park Archives.

In 1969, Elizabeth Kubler-Ross described the “five stages” of acceptance:  denial, anger, bargaining, depression, and acceptance. For many years, climate change discussions seemed to be about getting our politics past the “denial” stage. Over time, however, scientific inquiry made it obvious that climate change is happening and that it is the result of human activity. With more than 97% of climate scientists and every major scientific body of relevance in the United States in agreement that the threat is real, not to mention a similar consensus internationally, it became untenable to simply refuse to accept the reality of climate change.

The next stage was anger. Unable to stand on unvarnished denials, skeptics lashed out, alleging conspiracies and secret plots to propagate the myth of climate change. In 2003, Senator Inhofe from Oklahoma said, “Could it be that man-made global warming is the greatest hoax ever perpetrated on the American people? It sure sounds like it.” In 2009 we had “climategate.” More than a thousand private emails between climate scientists were stolen and used in an attempt (later debunked) to show a conspiracy to fool the world.

Now, from the right, come signs of a move to bargaining. On 13 February, Senator Marco Rubio reacted to the President’s call for action on climate change, but he did not do so by denying the phenomenon itself or accusing the President of having being duped by a grand hoax.  He stated instead, “The government can’t change the weather. There are other countries that are polluting in the atmosphere much greater than we are at this point. They are not going to stop.” Earlier this month he made even more promising statements: “There has to be a cost-benefit analysis [applied] to every one of these principles.” This is not anger or denial. This is bargaining. As long as others are not doing enough, he suggests, we get to ignore the problem.

It is, apparently, no longer credible for a presidential hopeful like Senator Rubio to deny the very existence of the problem. His response, instead, invites a discussion about what can be done. What if we could get the key players: Europe, China, India, the United States, and Russia to the table and find a way for all of them to lower their emissions? If the voices of restraint are concerned that our efforts will not be fruitful, we can talk about what kinds of actions can improve the climate.

To be fair, Senator Rubio has not totally abandoned denials. While engaging in what I have called “bargaining” above, he also threw in, almost in passing, “I know people said there’s a significant scientific consensus on that issue, but I’ve actually seen reasonable debate on that principle.” In December he declared himself “not qualified” to opine on whether climate change is real. These are denials, but they are issued without any passion; his heart is not in it. They seem more like pro forma statements, perhaps to satisfy those who have not yet made the step from denial and anger to bargaining.

If leaders on the right have reached the bargaining stage, the next stage is depression. What will that look like? One possibility is a full embrace of the science of climate change coupled with a fatalistic refusal to act. “It is too late, the planet is already cooked and nothing we can do will matter.”  When you start hearing these statements from those who oppose action, take heart; we will be close to where we need to get politically. Though it will be tempting to point out that past inaction was caused by the earlier stages of denial, anger, and bargaining, nothing will be gained by such recriminations. The path forward requires continuing to make the case not only for the existence of climate change, but also for strategies to combat it.

The final stage, of course, is acceptance. At that point, the country will be prepared to do something serious about climate change. At that point we can have a serious national (and international) conversation about how to respond. Climate change will affect us all, and we need to get to acceptance as soon as possible. In short, climate change will tear at the very fabric of our society. It will compromise our food production and distribution, our water supply, our transportation systems, our health care systems, and much more. The longer we wait to act, the more difficult it will be to do so.  All of this means that movement away from simple denial to something closer to acceptance is encouraging.  The sooner we get there, the better. (Oxford University Press Blog, Feb. 16, 2013)

At the moment, the United States is in the midst of one of the worst droughts in American history. One consequence is that the water level of the Mississippi River has fallen to the point where the river itself may have to be shut down to shipping traffic. What would a shutdown mean? Well, consider that 60 percent of all grain exported from the United States travels on the river. Or that over a period of a couple of weeks the river carried goods through St. Louis that would fill 500,000 semi trucks. In other words, we have no workable substitute for the river.

While droughts are not permanent events, even a temporary shutdown will cost thousands of jobs and billions of dollars. Perhaps more importantly, the changing climate ensures that there will be more droughts of this magnitude in the future. Rather than facing a problem like this once in a generation, we may face it every few years. It is difficult to imagine an impassable river every four or five years or, perhaps worse, for a couple of years in a row.

The federal government is aware of the danger and has stepped in to try to help. The Army Corps of Engineers is engaged in a dredging operation that will hopefully address the current crisis or, at least, delay the closure of the river. The longer-term problem, though, is the changing climate itself. We routinely divert resources in response to climate-related crises like this one, but we have yet to find the political will to curb emissions of greenhouse gases that are warming the Earth. In this sense, we are treating the symptoms rather than the disease. The more the planet warms, the more we will face crises like an impassable Mississippi or a Hurricane Sandy. Is our best plan really to suffer more and more harm each year and to spend more and more money trying to respond in a short-term way to crises generated by climate change? Shouldn’t we be treating the climate change disease itself by reducing emissions of greenhouse gasses? (Huffington Post, January 9, 2013)

Guzman (Law/Univ. of California; How International Law Works, 2010, etc.) writes that climate change is “perhaps the greatest international challenge of this century and beyond,” yet “people have not come to accept how serious it is.” By focusing on the human cost of global warming, his hope is that people will act. What will happen, Guzman asks, if the Earth’s temperature rises—and this is a conservative estimate—a mere 2 degrees centigrade? Plenty, as it turns out, and none of it good. A series of well-researched and clearly written chapters outlines the consequences. Rising seas will cause some nations, such as the Maldives, to simply sink. In other poor, low-lying nations, flooding and increasingly violent storms and the subsequent social disruption may create untold millions of “climate refugees”—20 million in Bangladesh alone. As glaciers melt, ancient water-management systems will be disrupted as new patterns of flood and drought emerge. Fresh water will become scarcer, and perhaps more than 1 billion people will have access to far less water than they do now. As climate refugees huddle together in inevitably crowded camps, new diseases will emerge with fewer resources to treat and prevent them. The social and political costs will be enormous; governments will be overwhelmed by the failure of basic systems, from food production to sanitation. Those areas of the world—say, the Middle East or Pakistan and India—already dangerously enmeshed in enmity may explode into violence as the battle for resources, especially water, intensifies. Though exact scenarios are difficult to predict, such dangers, notes Guzman, are real. But global warming is not unmanageable if we can simply muster the political will to enact and enforce regulations limiting greenhouse gas emissions.

A disturbing yet realistic examinations of the consequences of a warmer world. (Kirkus Book Review, December 17, 2012)

Hundreds of millions of gallons of raw and partially treated sewage from crippled treatment plants have flowed into waterways in New York and New Jersey, exposing flaws in the region’s wastewater infrastructure that could take several years and billions of dollars to fix.

One could be forgiven for seeing this as just one more article identifying the harms from Sandy, but I think it illustrates something else. If you had known in advance that Sandy would hit the Northeast as it did, the chances are good that you could have predicted many of the consequences. It was no surprise that power went out, that houses were damaged and destroyed, that people were stranded, and so on. You might not, however, have immediately thought about a failure of the sewage system. Yet this particular consequence will be among the most long-lasting and expensive to emerge from Hurricane Sandy.

The systems in New York and New Jersey failed because sewage plants were flooded by massive storm surges. The ultimate problem, though, was not the flooding itself, but rather how it affected the plants. It caused them to shut down, which, in turn, caused enormous amounts of raw sewage to flow where it is not supposed to go. In short, the sewage system failed.

Part of the problem, of course, is that the sewage plants in the region were built for a climate that is no longer with us. They are ill-suited for the more powerful and destructive storms that will be a regular part of life from now on. Without major investments, the next storm will have the same kind of damage and will expose millions of people to health risks.

We need to be concerned about more than just sewage systems, though. The sewage problem in New York and New Jersey is just one manifestation of a larger danger. Once we start to think about how climate change can undermine the basic structures we have built and upon which we rely, it becomes clear that virtually everything is at risk. Entire urban transportation systems can be paralyzed when tracks, equipment, or key subway stations are badly damaged. National transportation systems rely on ports that can be disabled or destroyed by storms. Power and communication systems are obviously vulnerable, as Sandy demonstrated. Agriculture can be affected as salt water from rising seas destroys productive land. Water systems in much of the country are also at risk. In California, for example, a failure of levees in Northern California — something made much more likely as seas rise — could cause salt water to rush into the Sacramento-San Joaquin Delta and shut down freshwater supplies to twenty million Californians for months. You get the idea.

The lesson here is that we need to see climate change as more than simply a series of weather events that will cause the same kind of harm that weather always causes. Though the direct damage caused by disasters like hurricanes Katrina, Irene, and Sandy or the 2012 North American drought are devastating, they are only (to use a climate-change-relevant metaphor) the tip of the iceberg. Each such event puts a strain on the basic infrastructure upon which we rely for our daily lives: sewage, health care, food, water, transportation, communication. Sometimes these systems will be strained enough to fail, and when they do, as happened to sewage systems during Hurricane Sandy, costs (both human and financial) skyrocket.

So the next time someone discusses the costs of climate change, if they don’t confront the reality that our infrastructure is not ready, you can be sure that they are leaving out a lot — perhaps most — of the costs we will actually face.

Andrew Guzman’s most recent book, Overheated: The Human Cost of Climate Change (Oxford University Press) is due out in February. (Huffington Post, December 17, 2012)

“Overheated provides a lucid vision of the catastrophic consequences we will face if we fail to transition away from a fossil fuel-based economy. What gives the book power is the perspective it provides, of a legal scholar who initially viewed climate change as an interesting topic for academic research, to a passionate advocate for tackling the greatest threat human civilization has yet faced. If you care about the future of our planet, read this book.”     

Michael E. Mann  |  Director of Penn State Earth System Science Center and Author of The Hockey Stick And The Climate Wars

“Andrew Guzman offers a concise and useful over view of the kind of problems a heating world will encounter—indeed, already is encountering. There’s nothing alarmist here—just straight forwardly realistic, and hence all the scarier”​

Bill McKibben  |  Author of Earth: Making A Life On A Tough New Planet

The chain of events here is relatively simple.  Climate change is already affecting societies around the world and those impacts will only get larger over time.  The developments intersect with security concerns because they tend to destabilize social structures, put pressure on resources (e.g., water, energy, etc), and exacerbate existing tensions among groups.  This is why climate change is often called a “risk multiplier.”  It is not likely to create security threats where none previously existed, but it is virtually certain to make existing threats more severe.  Put differently, if you think of a national security issue that concerns the United States, climate change is probably making it a larger, rather than smaller, problem.  This is true of the Middle East, where a warming world will magnify stress related to water issues; it is true of South Asia where melting glaciers will challenge the ability of India and Pakistan, both armed with nuclear weapons, to share water from the Indus River; and it is true in Africa where drought and rising temperatures will make it more difficult to prevent the rise of extremist groups, some of which threaten the United States.

The NRC report stops short of proposing policies aimed at preventing climate change because its authors do not view it as their task to engage in that form of policy recommendation.  The report is, instead, an attempt to “better assess [risks related to climate change] and to anticipate changes in them.”  Anyone interested in broader policy questions, however, cannot help but draw from this report the lesson that reducing the speed and extent of climate change needs to be viewed as a real national security imperative.

When it became clear to the United States that Al Qaeda posed a threat to the country, resources were devoted to meeting this threat.  Nobody argued that efforts to disrupt and defeat terrorist groups should be delayed until we learned more about their plans or until the specifics of the threat became clearer.  Nobody argues that we should ignore the rise extremist elements or efforts by terrorist groups to recruit supporters.  Whatever disagreements we have with respect to our response to terrorism, nobody believes that simply ignoring the issue is the correct strategy.  We should have these same attitudes toward climate change.  Just because the threat to our security comes from changes in the environment rather than from human enemies does not make it any less real.  The United States needs to acknowledge the very real danger that climate change poses to our security, and it needs to react not only by preparing for that threat, but also by reducing the speed with which the world is warming. (Legal Planet, November 16, 2012)

The book is at its best in these moments, dealing directly with the effects higher temperatures have on specific communities. Californian farming, reliant on accumulated snow for watering plants, will suffer if weather systems continue to change; an indigenous Bolivian community (the Uru Chipaya) that thrives on glacial runoff will be forced to alter its livelihood as glaciers melt at an expedited rate; and the disaster in Darfur is linked to a drought that threw Sudanese coexistence into devastation.

Guzman advocates global cooperation to reduce the rate of greenhouse gas emissions and prevent “the most severe effects of a warming world.” Although the book falters with some less grounded examples regarding disease, Guzman’s argument is thoroughly researched and will discourage doubters. (Publishers Weekly, November 5, 2012)

Clear, cogent, and compelling, Overheated shifts the discussion on climate change toward its devastating impact on human societies. Two degrees Celsius seems such a minor change. Yet it will change everything.