In the second of his two-part posting, veteran Denver broadcast meteorologist Mike Nelson outlines how he reached his views on human-caused climate change.

Having addressed a number of factors that have greatly influenced my thinking about human-caused climate change, I’ll next turn to some additional thoughts on the subject …

The Fate of the Arctic Ice

Another major complication for our future climate will be the fate of the sea ice in the Arctic. Satellite measurements since the late 1970s have shown that the sea ice had dramatically diminished and has reached a record low as of late summer 2012.

Although sea ice does grow and shrink as a result of natural cycles, the current state of the ice is near historic lows. Anecdotal records from indigenous peoples and 19th century sailors show that the melting of the ice, as well as the surrounding permafrost, indicate a dramatic warming of the northern latitudes.

The sea ice is highly reflective, and dark open ocean is just the opposite. As more of the Arctic Ocean remains open and ice-free, the waters will warm and play a major role in altering the phases and intensity of many ocean circulations.

These ocean patterns are complex, and it is not easy to predict the exact time when they will shift from one phase to another. The phases may not match up exactly from one ocean to the next, and the intensity varies. These are important factors in influencing the natural variability we see in the world’s climate.

Researchers are using the most sophisticated satellites, instruments, and super computers to try to learn as much as possible about the interactions of these oscillations and their role in our future climate.

NCAR’s New Super Computer

One of the most powerful computer systems is now operating just south of Cheyenne, Wyoming, at the new National Center for Atmospheric Research (NCAR) Super Computing Center. This center has 20 million times the computer power of the original CRAY 1 supercomputer that was installed at NCAR in the 1970s.

This new system will be able to do 1.6 quadrillion calculations per second, enabling researchers to run very complex models in a much smaller amount of time. With this new capability, climate researchers will be able to get a much better handle on the impact of the various ocean oscillations and their role in regional and global climate.

Researchers will also be able to get an idea about how global warming may change the intensity and frequency of these circulations.

Effects of El Niño and La Niña …

We are now in a neutral period that could swing back toward El Niño conditions. Mike Baker at the Denver-Boulder National Weather Service (NWS) office has put together an excellent resource on impacts El Niño might have on our weather.

These periodic warming and cooling events in the ocean need to be taken into consideration over the long term, not used as singular examples of a change in the climate. However, as Earth’s overall temperature increases, it is quite possible that we will see stronger versions of both El Niño and La Niña. The result will be increasingly severe individual episodes of heat and drought, storms and floods.

Frequently Asked Questions

There is much discussion in some climate “skeptics” corners about the role of the Sun in influencing Earth’s temperature. But the Sun certainly has not been overlooked by the many experts worldwide studying climate change. Just the opposite in fact.

The periodic changes in solar output and the orbital changes are taken into account in climate studies and modeling. In fact, the current solar output is slightly less than in previous decades — our climate should be cooling, but it is not.

Another comment often heard is that CO2 is just a trace fraction of the atmosphere. That’s the case, but simply because CO2 is a trace gas does not mean that it is not important in the equation. Small amounts do matter — I weigh 200 pounds, I require a certain small amount of vitamin D to remain healthy. Too much of this vitamin, however, and I will become very ill.

The vast majority of climate scientists are in agreement that the overall warming of the planet (about 1.5 degrees Fahrenheit since 1900), has been caused in significant part by mankind. This warming clearly results from our combustion and increased emissions of so called “greenhouse gases” — such as CO2, methane and CFCs (chloro-fluorocarbons).

These gases absorb outgoing heat from our planet and “reflect” it back to Earth. When this happens, energy from the Sun is trapped in our atmosphere, and our climate warms.

Think of each molecule of carbon dioxide like a feather in a down comforter. If there are not very many feathers, your body’s heat will escape through the comforter and you will be cold. If you keep adding feather after feather, the comforter becomes much more efficient at holding in your body heat … and you stay warmer. Our atmosphere behaves in a similar manner.

The Greenhouse Effect …

As often noted, the Greenhouse Effect is normal and natural; in fact if not for this effect, Earth would be about 60 degrees Fahrenheit colder — a lifeless ice planet. The problem we face is that the delicate balance of temperature may be upset by a change in atmospheric chemistry.

In the past 200 years (since the Industrial Revolution) the increased burning of fossil fuels has released vast amounts of carbon dioxide into the atmosphere. The atmospheric concentration of CO2 has risen about 25 percent in the past two centuries from 280 parts per million to nearly 400 parts per million.

Human activity releases about seven billion metric tons of this long-lived carbon dioxide into the air every year, adding to the 750 billion metric tons that are already there.

Of the seven billion tons, only about three billion tons stays in the atmosphere; the rest is absorbed by plants and the oceans. This “carbon sink” capacity complicates the issue of global warming, because the oceans have had a vast holding capacity for CO2. The oceans are becoming more acidic, however, and there is growing concern that this carbon sink capacity may reach a limit.

In addition, the greater acidity of the oceans is detrimental to the health of coral reefs that serve as the breeding grounds for thousands of sea creatures and is vital to the overall food chain.

Climate Has Always Changed

It is absolutely true that the Earth’s climate has cycled through great changes over the course of our geologic history. These changes are obvious in the fossil record — my home town area of Denver was once under a great shallow ocean. These changes result from a variety of causes, from volcanoes to continental drift to the shift in Earth’s orbit on its journey around the Sun, to changes in the output of energy from the Sun.

One of the key components to our Ice Ages has been what are called Milankovitch Cycles. These long-term changes in the shape of our orbit and the shift in the tilt of the Earth work like the complex gears of a clock, gradually switching our planet from Ice Age to warmer periods and back again.

The Milankovitch Cycles are well documented and have been a primary driver of our changing climate for hundreds of thousands to millions of years.

Now, for the first time in the Earth’s history, there is evidence that these gears may be impacted by changes in the atmospheric chemistry — changes that are being caused by human activity.

What about Cosmic Rays?

The theory that a change in climate might be related to cosmic rays has been in the news recently after the European Organization for Nuclear Research (CERN) published a paper about the relationship between cosmic rays and cloud formation.

The theory is that these invisible, high-energy rays could increase cloud cover and thus cause an increase in the reflection of sunlight, thus cooling Earth during the day. In contrast, the clouds could cause a warming at night by trapping the previous day’s heat.

The research is interesting, and it is well worth considering how an increase or decrease of these rays might impact the Earth’s climate. According to work published at, the observed changes in cloud nuclei were too small to have a significant effect on climate. In addition, in looking at trends in cosmic ray cycles, there is no connection that would fit with the increase in global temperature.

The CERN research is occasionally brought up by skeptics of human-caused global warming precisely because CERN has such a strong reputation for advanced research. It sounds exotic enough to be mis-represented as a legitimate natural cause for the warming we are seeing.

Upon further review, it appears that while it is excellent research, it is not a major driver of the current warming.

My Personal Thoughts …

I am not a climate scientist; my expertise lies in a much, much shorter timeframe. However, I spend a great deal of time on-line and at seminars with many of the best climate scientists from Boulder-based NCAR and other research institutes from around the world.

My conclusion from my studies is that we humans are indeed having a measureable impact on the warming of our climate, and these impacts are making weather events more extreme. With a greater amount of energy in the climate system, there will be drier droughts, heavier rains (although more spotty), bigger winter storms, and more powerful and severe weather events.

Remember, 90 to 95 percent of what we see is within the normal variability of weather — but it is that extra 5 to 10 percent, the “steroid” effect, that is making a drought just a little drier, a heat wave just that much hotter, a winter just slightly less cold.

Political Science vs. Climate Science

The topic of climate change has been given much political attention and in that light, there is a seemingly large controversy about what is happening and to what extent mankind is helping to cause some of the changes. In the strict world of truly peer-reviewed science, however, the degree of controversy is not nearly so great as some would have you believe.

The American Meteorological Society (AMS) is the oldest and largest professional society for weather and climate researchers. Here is a link to the latest AMS Statement on Climate Change. Although I would have preferred some stronger language on the natural variability of our climate, I agree with the AMS assessment on the whole.

Waxing Philosophical

My mother was a heavy smoker in the 1960s. As a child, I remember seeing white-coated purported scientists who claimed that there was no definite link between smoking and lung cancer. I lost her to that disease seven years ago.

My sister spent a lot of time in tanning booths in the 1980s. Again, there were plenty of “experts” who maintained that the rays from the tanning beds were different and actually “good” for us. She is now fighting stage 4 melanoma.

It is okay to have differing opinions — it is even a good thing, if the motives are purely science-based.

It is very important that we study this topic with even greater effort in order to be able to take appropriate actions for the future. This action may well be to use technology to bring ever-increasing efficiencies to our society. Through a more efficient use of our fuels, we will be able to limit the amount of greenhouse gases released, while still enabling our complex technological society to function and thrive.

Our choice, as Americans and as citizens of Earth, is to decide what priority we assign to this 5 to 10 percent change in our climate. Where does this fit into the decisions we must make for our future energy and environmental policies?

Our Very Special Planet …

When the Soviet Cosmonaut Yuri Gagarin, the first human in outer space, reached the top of our atmosphere and gazed out of his small porthole, he was terrified. He was not worried about his spacecraft, but he was shocked by how thin and fragile our atmosphere appeared against the cold blackness of space.

Gagarin later explained that he had always been taught that we lived at the bottom of a “great ocean” of air. From his Vostok 1 spacecraft, the ocean looked more like a shallow puddle.

As far as we know, out of the vastness of the universe, the planet Earth is the only place that harbors life. Someday we may find other worlds that provide an environment gentle enough to enable life to form, but for now, this is it, our lonely outpost in the remote corner of an entirely usual galaxy.

It seems prudent, patriotic, and reverent that we do what we can to conserve and protect the fragile envelope of air that allows us to live on planet Earth. The legacy we leave future generations depends upon the actions we take in the coming years. Our heirs will be the judges of our successes and of our shortcomings.

We will need to urge our leaders to take action to inspire the development of both new and cleaner ways to produce energy. Whatever the outcome of continuing science dialog and debates, we will still be better off, as will our grandchildren for whom we will have helped advance the technology to produce cleaner, renewable and more varied energy sources.

Reducing pollution and the dependence on foreign energy sources is something upon which all Americans can find common ground.

In the words of Thomas Jefferson in 1789, “I say the Earth belongs to each generation during its course, fully and in its own right, and no generation can contract debts greater than may be paid during the course of its own existence.”

Editor’s Note: This is the second of a two-part reposting, with permission of the author, broadcast meteorologist Mike Nelson of Denver. Part 1 was published on April 10. Reposted with light edits and with permission of the author.