I asked a climate scientist at NCAR, Caspar Ammann, to review the previous blog, and he brought up some interesting points that I thought I would talk about a little bit further. I am hoping this will inspire some of you to play with the data a little bit, in order to get a better “feel” for what makes the trends at the GLOBE sites “uncertain.”

The effect of extreme values on the trend line

Let’s start with the Jicin, Czech Republic, annual average temperatures. But this time, we will include 1996:

Figure 1. For GLOBE data at 4. Zakladni Skola in Jicin, the Czech Republic, change of trend from leaving out the first point.

In the figure the red points are those used for Fig. 2 of the previous blog. You see the trend, 0.04 degrees Celsius per year. If we add the point from 1996, the trend more than doubles – to 0.1 degrees Celsius per year – 1 degree Celsius per decade.

But 1996 might be a cold year. Remember – weather and climate vary from days to weeks to years to decades.

2001 was a cold year, too, relative to the surrounding points. What if we left 2001 out? How much would you expect 2001 to affect the trend? Note in Figure 2 that there is almost no effect. This is because 2001 is close to the middle of the data record. This makes sense: if you drew a straight line through the points by eye, you would be influenced more by the points at the beginning and end of the time series.

Figure 2. For same dataset, but ignoring the cold point in 2001.

Now, you might think that you should get rid of both years. Maybe they are not representative of the long term trend. Something happened in the Jicin area to make it a really cold year in 1996, and a really warm year in 2001. So, you plot the data without either of the two points.

Figure 3. Same data as for Figures 1 and 2, but minus the averages for 1996 and 2001.

Now we are back to the trend in the first graph – 0.04 degrees Celsius per year!

Someone might look at Figure 3, and say that the average temperatures are just going up and down with time, like the seasons. And, that the trend is just because you didn’t have two (or three, or four) complete oscillations! You couldn’t really say this person isn’t right without having temperature measurements from before 1996.

Obviously, the actual value of the temperature trend depends on how you look at the data! You might try this exercise for other stations in the data provided in the last blog.

Let’s try this exercise for the global points in Figure 7 of the last blog:

Table: Global Annual Average Temperature minus the 1961-1990 Mean. Source, Climate Research Unit, Hadley Centre, UK.

(The alert reader will notice that Figure 7 in the previous blog is slightly different now – I had accidentally included data for 2008, which is incomplete.)

Figure 4. For the most recent 12 years of the Hadley Climate Research Unit data, the effect of ignoring “extreme” points in the time series.

Note from Figure 4 that the slope varies depending on the data selected, but that the trends remain positive.

Reducing the influence of extreme points by smoothing

Recall last time that I took out the seasons because I thought they might affect the trend. Climate scientists average in time to get rid of the effect of large year-to-year changes like the ones in 1996 and 2001.

To show the effect of smoothing the data for Jicin, I will do a “three-point running mean average.” This means that I will average the first three temperatures and the first three years. That is, I will average

7.7500
8.8500
9.2300 to get 8.61

And I will average the years, too

1996
1997
1998 to get 1997

Then I will average the next three temperatures for 1997, 1998, and 1999 to get the temperature for 1998, and so on. Let’s say how this smoothing affects the data

Figure 5. For Jicin data, change in trend from smoothing the data.

And you might want to try four-point averages or five-point averages. The fact that the trend is positive, no matter what we do, gives us a little more confidence that there is a warming trend. Just as adding more stations would. But no matter how good the data in Figure 4, this is a trend only for one place – and only for 12 years.

Defining the average temperature

Unlike trends, which are affected by where the numbers are in time, the year doesn’t matter when you take an average. The larger the number of points, the less difference an odd year makes. Let’s do the averages for Jicin, starting with 2 years, then three years, then four years, and so on, for the complete record, to see how each new year affects the average temperature. The results are in Figure 6

Figure 6. For the Jicin data set, the average as a function of the number of points. To take the average, we start by averaging 1996 and 1997 (two points), then 1996, 1997, and 1998 (3 points), and so on.

As you can see, even the large changes at the end don’t really show up much in the average. And I think you can also see that, the more points in the average, the less one difference one more point will make.

Climatologists have chosen to take their average over 30 years. Thus the HAD.CRUT3 curve in Figure 7 of the last blog is relative to a thirty-year average – from 1961 to 1990.

The cost of using fossil fuels has gone up – we paid over $4.00 a gallon for gasoline for the first time this weekend. But of course there is the no-longer-hidden cost of what the carbon dioxide and other greenhouse gases released to the air when the fuel is burned do to our climate.

Figure 1. Watching the gas prices get higher than the milk prices. (Left) 5 March 2008; (Right) 15 May 2008. The four-dollar gasoline was purchased in Nebraska.

People are starting to respond sensibly, if slowly, by developing more efficient ways to extract power from fossil fuels or other sources in our environment. There is talk of cleaner coal and gas power plants, and making hydropower more efficient. Nuclear power is being considered more seriously. And we are developing new ways to get the energy we need. Among these are biofuels (for transportation), solar power, power from tides, geothermal, and wind power.

This weekend, I had the opportunity to drive through a large wind farm in northeastern Colorado, whose location you can find from the maps below.

Figure 2. (Left) location of Colorado. (Right) Location of Peetz.

The “wind farm,” near Peetz, Colorado, can generate up to 400 megawatts of energy. This makes the Peetz wind farm the second largest in the United States at this time. 400 megawatts is sufficient to power 120,000 homes in the U.S. There are 267 wind turbines, which cover an area that stretches for miles. It was fun to find out that oil is being pumped from the same land (Figure 3). Germany produces the most wind energy on Earth, with the U.S. second. According to the Global Wind Energy Council, wind power grew an average of 28% per year in the decade ending in 2006.

Theoretically, wind can be used to meet much of the world’s energy needs. But what of the negative side?

Many are worried about wind turbines killing birds. Current estimates of bird deaths from turbines run into the tens of thousands (U.S. statistics). To put this into perspective, many more birds are killed by collisions with automobiles, transmission towers, power lines, and windows. Such statistics aside, the danger to breeding populations, particularly of bird species that are no longer abundant, needs to be understood and considered.

But there are additional concerns. How do wind turbines themselves affect the weather and climate? Believe it or not, people are actually thinking about this. Also, the wind doesn’t blow all the time, so either a method is needed to “store” the energy, or we would have to use energy from another source when the wind isn’t blowing. Also, some people think that wind turbines are ugly (though others think they are beautiful).

Would you want a wind farm in the countryside or sea shore near you?

One more thing to think about. While higher energy prices make it harder for us to pay our bills for electricity, heating, and gasoline; high prices for energy also mean that industry will be more willing to develop new ways of extracting energy. Or, industry may be more willing to invest in figuring out ways to make conventional sources of energy more efficient. And higher energy prices make us more interested in using energy more efficiently by taking simple steps like turning out lights when we are not in the room, wearing a sweater and keeping the inside temperature cooler in the winter, and walking or taking the bus instead of driving.

Figure 3. A new and growing source of power – wind turbines, surrounding an oil pump (“pump jack”), representing a more traditional source of power. Near Peetz, Colorado, U.S.A.

Not only are Mauna Kea and Mauna Loa on the Island of Hawaii, but the “big Island” also has more petroglyphs than the other Hawaiian islands, and some spectacular waterfalls. Petroglyphs are images carved in stone. The age of these petroglyphs is not known, but experts believe the stick-figure petroglyphs are among the oldest.

The sulfur fumes that Gage was describing probably come from one of the volcanoes on the island. Based on measurements, water vapor is the most common gas coming out of volcanoes, with carbon dioxide second, and sulfur dioxide third. Also released are hydrogen, carbon monoxide, and hydrogen sulfide, and other gases. Both sulfur dioxide and hydrogen sulfide have strong smells and irritate the respiratory tract. Sulfur dioxide also irritates the eyes and skin, and sustained exposure to high concentrations of hydrogen sulfide and cause illness. One or both of these are probably the “sulfur fumes” in the blog, so it’s not surprising that the students changed their lunch plans.

Day 6 - 16 October 2007

Madison - 13
SNI participant

We hiked out to the petroglyphs, made up to 1,000 years ago. They were carved into the pahoehoe that resulted from the lava flowing uphill. It is believed that the carvings signify family. We later went to Akaka Falls. It is 450 feet (137 m) tall, and very thin. It’s in a rainforest.

Connor
SNI participant

The symbols called petroglyphs have many meanings, there were pictures of stick figure people were most likely just that; people. Little dots were supposedly representing a baby born, and that they put the umbilical cords underneath them. There were tons of other symbols, but they are kind of hard to name.

Gage - 13
SNI participant

We went to a place where there were petroglyphs carved into the lava, it was pretty cool. Then we had to move our lunch place because there was a ton of sulfur fumes in the place we were supposed go, so we had lunch in a parking lot. Tomorrow we fly back to Honolulu on Oahu again.

Recently, I posted the Hawaii record that showed that carbon dioxide has been increasing for the last several decades. To make the plot consistent with the global temperature plot, I showed only annual averages. Now, I show a copy of that same plot with seasonal information included.

Figure 1. Concentration of carbon dioxide at Mauna Loa, Hawaii (inset). NASA graph by Robert Simmon, based on data provided by the NOAA Climate Monitoring and Diagnostics Laboratory. Image from earthobservatory.nasa.gov/Newsroom/NewImages/…

This curve, which may be more familiar to many of you, has lots of wiggles. To look more closely at the wiggles, I obtained some data from the WLEF tower in Wisconsin, taken at 396 meters above the ground. The wiggles in Figure 2 show lots of variation from year to year, but there is a pattern. We can see the pattern easily if we average the data. During the winter, the carbon dioxide values are high. The values fall in the spring, and are smallest in July. By August, carbon dioxide values are increasing again.

What is happening? The WLEF tower is in a forest. During the spring and summer, the trees use up carbon dioxide in photosynthesis. As the trees leaf out, the carbon dioxide decreases. Once summer comes, photosynthesis starts slowing down, and so does carbon dioxide uptake. Like animals, both trees and the soils give off carbon dioxide in respiration. The curve shows the net effect of respiration and photosynthesis.

The carbon dioxide the tower measures does not just come from the forest – it can come from hundreds of kilometers away, and from grasses, shrubs, and crops as well as trees. Like the trees, these plants are also exchanging carbon dioxide with the atmosphere.

Figure 2. Monthly average flask values of CO2 from 396 meters above the surface. The inset shows the average for the ten years shown, to emphasize the change with seasons. Data collected by NOAA ESRL and The Pennsylvania State University and supplied by Ankur Desai (Dept of Atmospheric & Oceanic Sciences, University of Wisconsin-Madison).

Figure 2 is detailed enough to show lots of wiggles that don’t follow a smooth seasonal pattern. As the winds change, air with higher or lower values of carbon dioxide might be brought in. Where would carbon dioxide values be highest? Combustion produces carbon dioxide, so there will be higher values where there are lots of cars, factories, or fires. When trees are leafing out and growing, the carbon dioxide will be taken up. So it is possible that sharp peaks may be for times when the wind was bringing carbon dioxide from an area with lots of cities. Have you ever seen data on how much carbon dioxide is in the air near you?

(Note: We discuss carbon dioxide because it contributes to slightly over half of current greenhouse warming, but we must remember that methane, CFCs, ozone, and nitrous oxide together account with slightly less than half).

When I was a graduate student at the University of Washington, learning about weather and climate, I thought climate was boring, compared to tornadoes or thunderstorms. You averaged the temperature, rainfall, or wind, or – whatever – to get the climate of an area.

This changed around 1970, when I saw someone give a talk on the disturbing fact that the carbon dioxide in our atmosphere was increasing at a site on Mauna Loa in Hawaii. The speaker told us that he thought it was possible that this might make Earth’s climate warmer over time. (marked as “1″ on Figure 3). This was truly amazing! To me, the percentage of carbon dioxide was one of those numbers you memorized for class, like the conversion factor from Fahrenheit to Celsius. It was not supposed to change.

A few months later, another speaker said that the average global temperature, as far as he could see, would go down for a year or two after a volcanic eruption spewed dust into the stratosphere, and then warm up after the dust settled out. He didn’t think much else was happening.

Figure 3. Yearly average carbon dioxide concentration collected at Mauna Loa Observatory, Hawaii, USA. Data from C.D. Keeling and T.P. Whorf, and the Carbon Dioxide Research Group, Scripps Institute of Oceanography. Ppmv = parts per million by volume. For example 300 ppmv means that out of 1,000,000 molecules in the mixture of gases we call air, 300 are carbon dioxide.

In the meantime, the carbon dioxide kept increasing. In 1997, I worked for the first time with scientists who were measuring how much carbon dioxide was going between the surface and the air at a site near Wichita, Kansas, USA. To take this measurement, we needed a reference value for carbon dioxide, and we used “360 ppmv” (parts per million by volume). From this graph, we were clearly behind – the mean value had already gone up to 364 ppmv. In 2002, we took similar measurements in the same area, and I was surprised to see how much the value had changed in only five years.

The amount of carbon dioxide in Earth’s atmosphere has changed a lot over geologic time.

• At the end of the Permian period (about 250 million years ago) scientists have estimated that carbon dioxide in the atmosphere was a high as 10 times what it is today.
• During the mid-Cretaceous period, the dinosaurs also lived in a “greenhouse” world. Again, scientists estimate carbon dioxide could be as high as ~10 times what it is today.

Geologic evidence supports a warmer climate in both cases, especially in Polar Regions. This has a lot to do with the large changes that take place when snow disappears.