Astroblog: The Advertiser's War on Science

Tuesday, July 15, 2008

The Advertiser's War on Science

One of the things I'm passionate about is science communication. Understanding science, and its tools and methods, are critical for citizens to make informed decisions on issues from gene-modified foods to global warming. The need to understand and communicate science is highlighted by a recent column by Chris Kerry, of my local paper the Advertiser. In it he claims that global warming ended in 1998. Unfortunately, it hasn’t (see the graphs here and scroll down), but to understand why you need to know something about statistics.

First, let me reacquaint you with the Arrhenius equation, this says, for a given input of radiation, if you add more carbon dioxide to an atmosphere, it will warm up in a predictable manner. It’s standard physics, and you can readily calculate how much warmer the earth will get given the amounts of carbon dioxide we are injecting into the atmosphere. But why, you say, if this is simple physics, don’t we see a smooth rise in global temperatures? Because the climate record is noisy.

Superimposed on the CO₂ induced rise in temperature is noisy from a wide variety of sources, dust from volcanoes, heat shifts in the ocean from El Nino and La Nina events and a whole host so other sources. These effects put wobbles in the line that may be misleading if we don’t understand what is going on.

Have a look at the graph at the top left above, it looks like the graph starts off flat, rises somewhat then flattens out. Much like the graph Kerry refers to in his column.

But the illustration is in fact a relentlessly rising line. I have merely added some noise to it (for the technically minded I used RAND()*(-0.5-0.5)+0.5 to add random numbers ranging between -0.5 and 0.5 to the dataset). The graph below it shows the actual line that underlies the noisy data.

The graph below that again shows the actual temperature record from GIS TEMP,, how do we extract the underlying trend? What you don’t do is look at the last few data points. If you took the last 5 data points of my graph and look at the trend, it comes out nearly flat, yet we know that the curve is rising, you need to sample more pints to get a clear feel for the trend. In global warming data, you need to sample between 10-15 years to see the underlying trend, and that trend is relentlessly upwards.

So, no, global warming did not stop in 1998 and global temperatures have not dropped since 1998.

See also Did Global Warming Stop in 1998?, Global Trends and ENSO , and Wiggles. You may also find these links helpful. Global climate and the El Nino phenomenon. Doubts about the advent of spring.

Labels: global warming sillyness, science matters

# posted by Ian Musgrave @ 7:35 am

Comments:

Next time, please do not use GIS as your source of temperature data. There are so many problems with that database, that it has become almost useless.

For the most accurate global temperature databases, the RSS and UAH are obtained from satellites and are the most reliable.

For current plots of the RSS and UAH global temperatures, you can view them here:

http://wattsupwiththat.wordpress.com/2008/07/03/all-the-curves-that-are-fit-to-print/#comments

Of course, that data is available from multiple sources and you can make your own plots.

# posted by

Anonymous : 5:44 am

Doesn't matter if you use GISS or Hadley or whatever (if you had followed the links you would have seen this for several datasets), temperature is still climbing, this increase can be seen in the RSS data as well

# posted by

Ian Musgrave : 7:12 am

I am very happy that you took the effort to look at the satellite data.

As a scientist, this is what you should be doing. Trust, but verify!

I tried to warn you about the integrity of the GISS climate database. This is something that I do, because as a trained meteorologist, the data quality is horrifying.

I can not post images in this comment, but I can provide a link to an study of the "official" weather stations in the state of Main.

http://www.m4gw.com:2005/m4gw/2008/07/makin_up_climate_data_from_jun.html#more

Now for Australia and New Zeeland, we have also obtained documentation of a few of the "official" weather station.

I invite you and all of your friends, to take a camera and locate your local "official" weather station and document it.

This is what science is all about!

# posted by

Anonymous : 8:50 am

Ah heck, that link was clipped.

Try this one:

http://www.m4gw.com:2005/m4gw/

I live in Minnesota where the winter temps can get below -40 C.

We may tease and laugh, but there is a reason why I get so upset about crappy data.

As scientist, we should demand something better.

# posted by

Anonymous : 9:00 am