Humans today have differing views on what we have done to this planet, and what we might do to fix things. A commonly held view, however, is that whatever damage we have done is something that can be corrected by concerted action. Many don’t think that global warming is actually occurring, while others think that things are warming, but that humans haven’t caused it. Many think that sea level rise is the main unwanted consequence of global warming. And nearly all think that if we cut back on greenhouse gas emissions, we’ll cut back on warming. It is this last belief that I want to address here.

We are right to believe that greenhouse gases result in warming. Greenhouse gases, such as water vapor, carbon dioxide, and methane, work like a blanket around the planet: They absorb infrared radiation rising from the earth’s surface, the air, and the clouds, and radiate some of it back to earth. The average spot on earth would be about 0°F without a greenhouse effect, rather than the 57°F it now averages. Scientists have understood this effect since the 1800’s, and today’s scientists are unanimous in the view that increases in greenhouse gases will produce increases in the earth’s temperature.

We are also right to believe that humans produce greenhouse gases. Every exhaust pipe, power plant, smokestack, fire or farting cow produces greenhouse gases. And so studies of the level of greenhouse gases show that they began to rise slowly when humans entered the scene and began farming; they they rose faster as humans deforested, began raising livestock, and began cities; that they surged at the start of the industrial revolution, and that they are being produced in even greater quantities today.

We are right to think that the planet is warming, as evidenced by our drowning polar bears, our melting glaciers, and snowless winters. But we are also right to believe otherwise, for many good reasons. The actual warming has been slight so far — about 1.33°F in the last 100 years. This very slight increase over such a long time period (in human terms) is further masked by daily fluctuations and regional variations. For instance, some parts of the world are currently cooling, even though the world’s average temperature overall is rising. So anyone who trusts intuition, experience, or memory more than science is likely to remain skeptical that global warming is taking place.

Even for those who are willing to believe that the earth is warming, the notion that humans are causing this can be difficult, again for many reasons.

We all have a sense that we are puny, compared to the earth, and so how could humans have such a powerful effect? (Anyone flying across this country at night will see that we have lighted empty parking lots and empty ball fields and quiet suburban streets from coast to coast, and keep these lights on all night. They’ll see the congestion at rush hour, four lanes wide and stopped, with engines running. Perhaps collectively we are not so puny.)

We know that other forces can affect global temperature, including changes in the brightness of the sun, changes in the earth’s orbit, and volcanic eruptions. So it is possible that other factors are to blame, or have stronger effects than humans on what is happening.

We like to think that good people do good things, that good things happen to good people, and that people are good. This Pollyanna Principle makes it hard for us to accept that our species could be a planetary villain.

Those troubled by the notion that humans are causing global warming may draw strength from well-intentioned newspaper accounts. Reporters strive for “fairness”, giving “both” sides near-equal space in their stories. Fairness can be judged by column inches, but accuracy is harder to judge. A fair account of the shape of the earth might be to spend a few column inches explaining why some people think it is round (or “an oblate spheroid”), and then a few column inches explaining why others think it is flat. That seems silly, because today nearly everyone thinks it is round… but the typical global warming story falls into the trap, giving thousands of scientists a few column inches, and then a few lobbyists from the energy industries a near equal number. In fact, some 2,500 scientists from over 60 countries have reviewed 20,000 papers in scientific journals and concluded that the balance of evidence suggests a discernible human influence on global climate.

Finally, the skeptical laymen can draw strength from the normally skeptical scientist. Scientists are professionals at equivocation. Careers are built on split hairs. Wisdom is shown in failure to agree. So when climate scientists show any uncertainty about their forecasts, lobbyists can rejoice, finding support for their idea that the earth is flat.

Tipping Point?

But even if our global attitudes toward the problem were to suddenly shift, and in unison we acknowledged that things are changing, and from our own doing, we have one big problem left to address: the notion that we can fix it. If we slow our output of greenhouse gases, we’ll slow global warming, and avert tragedy. So goes our wishful thinking.

The notion that we can do anything if we put our minds to it helped get us to the shores of America, the shores of California, and the surface of the moon. But something stands in the way of fixing the planet: what scientists call a “positive feedback loop”. Such a loop happens when a system starts affecting itself, and a little perturbation feeds back, causing a bigger and bigger perturbation, and bigger and bigger effect. Such a loop likely exists with global climate, because the history of the earth’s climate seems to be one of fluctuating between quite warm and quite chilly, with little time spent in between. So perhaps the earth’s climate history has fluctuated when positive or negative feedback loops were triggered.

Positive feedback loops have not been given the attention they deserve by climatologists or the press, considering how potentially powerful they can be. But they are certainly easy for a layman to understand.

  • Albedo refers to the degree to which a substance reflects light. Snow and ice reflect light better than liquid water, and thus absorb less heat. Every bit of ice in the arctic thus helps keep things cool, and every bit of open water helps warm things further. Albedo plays a big role in helping an ice age keep its cool, and in preventing ice from even forming in warm periods, such as the Eocene. Warming an area that is covered in snow or ice does not have much local effect on temperature until that snow or ice begins to melt. But melting triggers a more rapid rise in temperatures, which mean more melting.
  • Permafrost is soil that is frozen year-round. Warming permafrost is no more dangerous than warming ice, but thawing permafrost is just as dangerous for global temperature as melting ice and snow, forming a similar feedback loop. In northern Alaska, the 4-7°F. warming that has occurred in the last century has still not reached a thawing temperature, but south of the Yukon River and on the south side of the Seward Peninsula, permafrost was thawing in 2003.
  • Methane is a greenhouse gas that is 20 times as potent in global warming as an equal amount of carbon dioxide. It is formed when plant matter decomposes without much available oxygen, such as under water or in an animal’s intestine. In May 2005, Katey Walter of the University of Alaska Fairbanks told a meeting in Washington of the Arctic Research Consortium of the US that she had found methane hotspots in eastern Siberia, where the gas was bubbling from thawing permafrost so fast it was preventing the surface from freezing, even in the midst of winter. In August 2005, Sergei Kirpotin and Judith Marquand reported that one million square kilometers of a frozen peat bog covering the entire sub-Arctic area of Western Siberia had started to melt in 2001 or 2002. New calculations showed the levels of methane emissions from northern wetlands 10 to 63 percent higher than the previous estimates. Larry Smith of the University of California, Los Angeles, estimates that the west Siberian bog alone contains some 70 billion metric tons of methane, a quarter of all the methane stored on the land surface worldwide. Massive methane release, which will warm the earth further, has been in progress for the past 5-7 years.
  • Drought and fire form another vicious cycle. When the water table drops and vegetation dries, fire becomes more likely. When vegetation burns, it switches from carbon sink to carbon source, releasing massive amounts of carbon dioxide, further warming the earth, further increasing the chances of drought. Many parts of the world, including Australia, Indonesia, the Amazon, and the American West and South, are experiencing epic droughts, and increasing probability of fire.

Each of these feedbacks push us to a tipping point of irreversible climate change, one from which no human actions can recover. With each, it is looking like the tipping point is not sometime in the near future, but has already occurred, some few years ago. If this is so, then the earth is subject to runaway warming and its effects — a little unexpected warming at first, and then more and more. The problem will not be a rise in sea level or destruction of habitat, but rather change that we cannot stop, no matter what we do. If the earth warms 10 degrees F as it is expected to, there will be no putting the genie back into the bottle.

One clue that the tipping point has already occurred: we are finding that our prior forecasts of higher greenhouse gas concentrations or warmer temperatures were too low — some unexpected factors have pushed things beyond what would have been expected from simple human population growth. A related clue: carbon dioxide is now building in the atmosphere faster than the human population has been growing recently. In recent years, atmospheric carbon dioxide has increased about 6.5% per year, compared with a human population increase of about 1.3%.

I hope that no tipping point has been reached. I would like to think that humans can throttle their carbon consumption and turn things around. But all of the evidence suggests otherwise. We need to consider this possibility, and need to report on the facts of global warming accurately, with less concern that we might offend the energy industry and its need for “fairness”. Our earth, after all, is not flat.

The notion that the planet’s climate has now reached a tipping point, and has begun to change on its own, is conjecture. We do not have first-hand experience with climatic tipping points, and few researchers have focused on them.  But there are reasons to think a tipping point has been reached:

  • Again and again, climate models have been proven to be too optimistic. For instance, a model forecasting temperature change from carbon dioxide levels might find that actual temperatures in the last decade have risen faster than the model predicted.  Such models, it could be argued, have omitted the positive feedbacks that bring us to a tipping point.
  • There is strong geological evidence that under conditions similar to the present, when greenhouse gases reached high levels, tipping points were triggered and climate changed dramatically.

Not Believable

The suggestion that a tipping point has already been reached, and the extreme changes in our climate have already been set in motion — irreversible motion — is not acceptable. Not believable. Here are some of the forces working against belief in such a notion:

  1. Humans as Superman.  People believe that when organized and motivated, humans can do anything. Anything broken can be fixed. Any problem can be solved.  So we can feed the planet if we just buckle down and work at it.  And we can reduce carbon emissions and thus stop global warming if we all pull together. And if there is a plausible plan, then things are as good as done.
  2. The Pollyanna Principle. People want good news. They prefer to hear good news. Too much bad news, and they just can’t handle news at all.
  3. Gradual change undetectable, unbelievable. If the world is warming, why were Britain’s last two summers so mild and damp?, some wonder.  Humans focus so much on day-to-day fluctuations that small shifts in average rainfall or temperature go undetected. And many choose to believe that what they cannot sense does not necessarily exist. Our planet is full of people who do not believe the planet is warming at all.
  4. Good people don’t do bad things. Us little humans couldn’t change the weather. Many folks want to find evidence of climate cycles or sun spots or anything that could account for observed climate change, in hopes of sustaining their belief that we are not at fault.
  5. Sudden change is unimaginable. Climate tipping points have been reached perhaps only 10 times in the last 100 million years. Why should we believe that one might happen (or have happened already) in our lifetime?
  6. Humans don’t do real math well. Regardless of our mathematical training, we don’t have any direct experience on things very big or very small.  One hundred million years doesn’t seem much longer than a thousand years, and a degree doesn’t seem like much at all. Most everyone has trouble with simple questions such as “what is the average temperature”, answering with “it depends…”. Too much variability (noise) and we lose the signal. And so a few cool days makes it harder to see a general increase in temperatures.

If we cut back on greenhouse gas emissions, will we stop global warming?  No.  If a climate tipping point has occurred, then there may be nothing we can do to stop the runaway train.  Has our climate reached a tipping point?  Is it now changing on its own?  I believe so.


  • Diamond, Jared. Collapse. How Societies Choose to Fail or Succeed. Viking. New York. 2005.
  • Gore, Al. An Inconvenient Truth. The Planetary Emergency of Global Warming and What We Can Do About It. Rodale. Emaus PA. 2006.
  • Lynas, Mark. Six Degrees. Our Future on a Hotter Planet. National Geographic. Washington D.C. 2008.
  • Pearce, Fred. With Speed and Violence. Why Scientists Fear Tipping Points in Climate Change. Beacon Press. Boston. 2007.
  • Ward, Peter D. Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future. Collins. N.Y. 2008.