Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100

could see was a long column of white ice. But upon closer examination, I could see that the ice had stripes made of tiny bands of different colors.
    Scientists have to use a variety of techniques to date them. Some of the ice layers contain markers indicating important events, such as the soot emitted from a volcanic eruption. Since the dates of these eruptions are known to great accuracy, one can use them to determine how old that layer is.
    These ice cores were then cut in various slices so they could be examined. When I peered into one slice under a microscope, I saw tiny, microscopic bubbles. I shuddered to realize that I was seeing air bubbles that were deposited tens of thousands of years ago, even before the rise of human civilization.
    The carbon dioxide content within each air bubble is easily measured. But calculating the temperature of the air when the ice was first deposited is more difficult. (To do this, scientists analyze the water in the bubble. Water molecules can contain different isotopes. As the temperature falls, heavier water isotopes condense faster than ordinary water molecules. Hence, by measuring the amount of the heavier isotopes, one can calculate the temperature at which the water molecule condensed.)
    Finally, after painfully analyzing the contents of thousands of ice cores, these scientists have come to some important conclusions. They found that temperature and carbon dioxide levels have oscillated in parallel, like two roller coasters moving together, in synchronization over many thousands of years. When one curve rises or falls, so does the other.
    Most important, they found a sudden spike in temperature and carbon dioxide content happening just within the last century. This is highly unusual, since most fluctuations occur slowly over millennia. This unusual spike is not part of this natural heating process, scientists claim, but is a direct indicator of human activity.
    There are other ways to show that this sudden spike is caused by human activity, and not natural cycles. Computer simulations are now so advanced that we can simulate the temperature of the earth with and without the presence of human activity. Without civilization producing carbon dioxide,we find a relatively flat temperature curve. But with the addition of human activity, we can show that there should be a sudden spike in both temperature and carbon dioxide. The predicted spike fits the actual spike perfectly.
    Lastly, one can measure the amount of sunlight that lands on every square foot of the earth’s surface. Scientists can also calculate the amount of heat that is reflected into outer space from the earth. Normally, we expect these two amounts to be equal, with input equaling output. But in reality, we find the net amount of energy that is currently heating the earth. Then if we calculate the amount of energy being produced by human activity, we find a perfect match. Hence, human activity is causing the current heating of the earth.
    Unfortunately, even if we were to suddenly stop producing any carbon dioxide, the gas that has already been released into the atmosphere is enough to continue global warming for decades to come.
    As a result, by midcentury, the situation could be dire.
    Scientists have created pictures of what our coastal cities will look like at midcentury and beyond if sea levels continue to rise. Coastal cities may disappear. Large parts of Manhattan may have to be evacuated, with Wall Street underwater. Governments will have to decide which of their great cities and capitals are worth saving and which are beyond hope. Some cities may be saved via a combination of sophisticated dikes and water gates. Other cities may be deemed hopeless and allowed to vanish under the ocean, creating mass migrations of people. Since most of the commercial and population centers of the world are next to the ocean, this could have a disastrous effect on the world economy.
    Even if some cities can be salvaged, there is still the danger that large storms can send surges of water into a city, paralyzing its infrastructure. For example, in 1992 a huge storm surge flooded Manhattan, paralyzing the subway system and trains to New Jersey. With transportation flooded, the economy grinds to a halt.
    FLOODING BANGLADESH AND VIETNAM
    A report by the Intergovernmental Panel on Climate Change isolated three hot spots for potential disaster: Bangladesh, the Mekong Delta of Vietnam, and the Nile Delta in Egypt.
    The worst