Bob Ryan on Global Warming, Part 2

Is climate really changing?

By BOB RYAN

Updated 8:33 AM EDT, Mon, Mar 9, 2009

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How do we observe the Earth, Weather and Climate?

First some definitions. Let’s call "Earth" our home planet and everything on and around it -- land, oceans, life, atmosphere. Weather and climate? I don’t know who said it first, but I like the definition of both as, “Climate is what you expect, weather is what you get.”

We can observe our Earth, weather and climate by just looking at the sky and Earth, but to make objective observations we need scientific instruments -- things like thermometers, wind vanes, barometers and, in the last 50 years, satellites. Wow, can we observe Earth and weather and climate like never before. Look at this first image in 1960 from the first weather satellite TIROS.

Courtesy NOAA

That was April 1, 1960. If you look close, you can see the Canadian Maritime Provinces on the right in this view over the Atlantic.

Here are some recent images from the current operational geostationary weather satellites of monster hurricane Katrina. NASA has some wonderful polar orbiting satellites (Aqua and Terra) that with an instrument called “MODIS” (Moderate Resolution Imaging Spectroradiometer) also give us terrific observations of our weather, climate and Earth

Courtesy NOAA/NASA

Courtesy NASA

What do you observe in the two satellite pictures above?

A very destructive hurricane in the GOES image. The GOES satellite observations are critical to helping meteorologists forecast the strength and path of storms. What about the NASA Aqua image from December 2003? What are those straight lines? If we did not know about airplanes or had not seen highflying jet planes creating a trail of white lines would we have any idea what those white lines are in the satellite picture? Well we have observed jet planes creating white lines of clouds in the sky ... white trails called “contrails.”

It appears most of the white we observe in the satellite picture are contrails (condensation trails) from jet airplanes flying over France, the English Channel and England. The jet exhaust includes water vapor which condenses and freezes in the high atmosphere and because the air is relatively humid (even at 30,000 feet) the contrails grow and fill much of the sky.

Here is an example, an observation by a satellite, where there is a change in the sky caused by something we humans have done. In this case, we have made airplanes, which fly 5-6 miles high and burn jet fuel and in the process of combustion-burning fuel produce and release tons of water. The clouds are not natural; they are produced by something we humans have done. These clouds are an “anthropogenic” change in the sky.

Earth at night from composite DSMP satellite images showing the human generated (anthropogenic) lights at night.

Courtesy NASA/GSFC and NOAA.

Anthropogenic is a word you will hear often in discussions and articles about weather, climate and global change science. But as you can see in the satellite picture over France, for at least one day, human activity had changed the weather. In this case, the cloud cover over western France. As shown above, satellites also show us how we are changing the night sky.

Observations, Ideas, Measurements, Errors and Uncertainty

All of us have measured and observed the temperature of the air or atmosphere. We use a thermometer to measure the temperature of the air but today satellites can use remote sensing tools such as infrared sensors to measure the temperature of the atmosphere from space. But it is not only measurements of temperature, wind, rain, pressure and humidity that we need in studying and thinking about weather, climate and changes in weather, climate and Earth.

Observations and Ideas

Here are some graphs of measurements or recorded observations of various things over about the same period of time. What do you think is being measured?

What is measured in these three graphs since about 1800 is the world population (middle graph), the average global temperature over land and water (bottom graph) and, in the top graph, the total amount of carbon dioxide that has been released into the atmosphere by burning fossil fuels (oil, gas, coal, wood).

When we see these measurements and observations, I think it is fair to say Earth is changing. There are about five times as many people in the world today as when I was born ... wow! The temperature of the world is changing. However, it has always been changing, and was changing before humans arrived.

Weather is just the current state of the atmosphere, and we know that each day the temperature pattern, sky, air movement is different so the weather is always changing. So by a few observations, I think we can fairly answer two of the questions in this article’s title. The weather is always changing -- that’s weather. Also, Earth is changing -- it’s a dynamic planet; it has been and always will be changing.

What About Climate?

When meteorologists and climatologists talk about “climate,” we are really talking about the “average” weather over some considerable period of time, on the order of decades or longer. Here in the U.S., for instance, the “average” high and low we show many days is defined as the 30-year average high temperature for that day. As you can see above and better here:

The global average temperature is changing, increasing in a bit of an uneven pattern from the long-term average, especially over about the last 30 years. But note the year-to-year fluctuation of the temperature and the uncertainty (vertical bars) in the measurements.

Before we go much farther, you should know that “uncertainty” in science does not mean “unknown.” Every measurement you or I make, everything we do (of course except death and taxes) has some uncertainty. The history of certainty and uncertainty in science is quite interesting. (http://books.nap.edu/catalog.php?record_id=10248)

What about that uncertainty?

Measuring the temperature, wind, humidity, ocean temperature, salinity ... whatever has some error or uncertainty, but as in the graphic example above we can, even with some measurement error, see that the blue line, the long-term average, is showing some general global warming trend over the last 130 years, even though there are periods that last a number of years that show cooling or near constant global temperatures.

Ideas

If you think you can see some correlation between the increase in the amount of carbon dioxide in the atmosphere and the slow, but irregular, increase in global temperature, you are not alone. But also, this is not a new idea.

What we call “The Greenhouse Effect” was first theorized and explained by the famous French mathematician Jean Baptiste Fourier almost 200 years ago. More than 100 years ago, a Swedish chemist, Svante Arrhenius, calculated the possible warming from the burning of fossil fuels just beginning with the Industrial Revolution. Pretty old ideas or scientific theories.

Ready to tackle the science of the Greenhouse Effect, carbon dioxide and global change?

OK Scarlett, tomorrow.