Short Answers to Hard Questions About Climate Change

1. 1.How much is the planet heating up?
   1.7 degrees is actually a significant amount.

   As of this October, the Earth had warmed by about 1.7 degrees Fahrenheit since 1880, when tracking began at a global scale. That figure includes the surface of the ocean. The warming is greater over land, and greater still in the Arctic and parts of Antarctica.

   The number may sound low, but as an average over the surface of an entire planet, it is actually high, which explains why much of the land ice on the planet is starting to melt and the oceans are rising at an accelerating pace. The heat accumulating in the Earth because of human emissions is roughly equal to the heat that would be released by 400,000 Hiroshima atomic bombs exploding across the planet every day.

   Scientists believe most and probably all of the warming since 1950 was caused by the human release of greenhouse gases. If emissions continue unchecked, they say the global warming could ultimately exceed 8 degrees Fahrenheit, which would transform the planet and undermine its capacity to support a large human population.

2. 2.How much trouble are we in?
   For future generations, big trouble.

   The risks are much greater over the long run than over the next few decades, but the emissions that create those risks are happening now. Over the coming 25 or 30 years, scientists say, the climate is likely to resemble that of today, although gradually getting warmer. Rainfall will be heavier in many parts of the world, but the periods between rains will most likely grow hotter and therefore drier. The number of hurricanes and typhoons may actually fall, but the ones that do occur will draw energy from a hotter ocean surface, and therefore may be more intense, on average, than those of the past. Coastal flooding will grow more frequent and damaging.

   Longer term, if emissions continue to rise unchecked, the risks are profound. Scientists fear climate effects so severe that they might destabilize governments, produce waves of refugees, precipitate the sixth mass extinction of plants and animals in Earth’s history, and melt the polar ice caps, causing the seas to rise high enough to flood most of the world’s coastal cities.

   All of this could take hundreds or even thousands of years to play out, conceivably providing a cushion of time for civilization to adjust, but experts cannot rule out abrupt changes, such as a collapse of agriculture, that would throw society into chaos much sooner. Bolder efforts to limit emissions would reduce these risks, or at least slow the effects, but it is already too late to eliminate the risks entirely.

3. 3.Is there anything I can do?
   Fly less, drive less, waste less.

   There are lots of simple ways to reduce your own carbon footprint, and most of them will save you money. You can plug leaks in your home insulation to save power, install a smart thermostat, switch to more efficient light bulbs, turn off the lights in any room where you are not using them, drive fewer miles by consolidating trips or taking public transit, waste less food, and eat less meat.

   Perhaps the biggest single thing individuals can do on their own is to take fewer airplane trips; just one or two fewer plane rides per year can save as much in emissions as all the other actions combined. If you want to be at the cutting edge, you can look at buying an electric or hybrid car, putting solar panels on your roof, or both.

   If you want to offset your emissions, you can buy certificates, with the money going to projects that protect forests, capture greenhouse gases and so forth.

   In the end, though, experts do not believe the needed transformation in the energy system can happen without strong state and national policies. So speaking up and exercising your rights as a citizen matters as much as anything else you can do.

   1. What’s the optimistic scenario?
      Several things have to break our way.

      In the best case that scientists can imagine, several things happen: Earth turns out to be less sensitive to greenhouse gases than currently believed; plants and animals manage to adapt to the changes that have already become inevitable; human society develops much greater political will to bring emissions under control; and major technological breakthroughs occur that help society both to limit emissions and to adjust to climate change.

      The two human-influenced variables are not entirely independent, of course: Technological breakthroughs that make clean energy cheaper than fossil fuels would also make it easier to develop the political will for rapid action.

      Scientists say the odds of all these things breaking our way are not very high, unfortunately. The Earth could just as easily turn out to be more sensitive to greenhouse gases than less. Global warming seems to be causing chaos in parts of the natural world already, and that seems likely to get worse, not better. So in the view of the experts, simply banking on a rosy scenario without any real plan would be dangerous. They believe the only way to limit the risks is to limit emissions.
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   2. 5.What’s the worst-case scenario?
      There are many.

      That is actually hard to say, which is one reason scientists are urging that emissions be cut; they want to limit the possibility of any worst-case scenario coming to pass. Perhaps the single greatest fear is a collapse of food production, accompanied by spiraling prices and mass starvation. Even with runaway emissions growth, it is unclear how likely this would be, as farmers are able to adjust their crops and farming techniques, to a degree, to adapt to climatic changes. Another possibility would be a disintegration of the polar ice sheets, leading to fast-rising seas that would force people to abandon many of the world’s great cities and the loss of trillions of dollars worth of property and other assets. Scientists also worry about other wild-card scenarios like the predictable cycles of Asian monsoons becoming less reliable. Billions of people depend on the monsoons to supply them with water for crops. So any disruptions to monsoons would have catastrophic consequences to those populations.

   3. 6.​Will a tech breakthrough help us?
      Even Bill Gates says don’t count on it, unless we commit the cash.

      As more companies, governments and researchers devote themselves to the problem, the chances of big technological advances are improving. But even many experts who are optimistic about technological solutions warn that current efforts are not enough. For instance, spending on basic energy research is only a quarter to a third of the level that several in-depth reports have recommended. And public spending on agricultural research has stagnated even though climate change poses growing risks to the food supply. People like Bill Gates have argued that crossing our fingers and hoping for technological miracles is not a strategy — we have to spend the money that would make these things more likely to happen.

   4. 7.How much will the seas rise?
      The real question is not how high, but how fast.

      The ocean is rising at a rate of about a foot per century. That causes severe effects on coastlines, forcing governments and property owners to spend tens of billions of dollars fighting erosion. But if that rate continued, it would probably be manageable, experts say.

      The risk is that the rate will accelerate markedly. If emissions continue unchecked, then the temperature at the earth’s surface could soon resemble a past epoch called the Pliocene, when a great deal of ice melted and the ocean rose something like 80 feet compared to today. A recent study found that burning all the fossil fuels in the ground would fully melt the polar ice sheets, raising the sea level by more than 160 feet over an unknown period.

      With all of that said, the crucial issue is probably not how much the oceans are going to rise, but how fast. And on that point, scientists are pretty much flying blind. Their best information comes from studying Earth’s history, and it suggests that the rate can on occasion hit a foot per decade, which can probably be thought of as the worst-case scenario. A rate even half that would force rapid retreat from the coasts and, some experts think, throw human society into crisis. Even if the rise is much slower, many of the world’s great cities will flood eventually. Studies suggest that big cuts in emissions could slow the rise, buying crucial time for society to adapt to an altered coastline.

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