Science: Global Warming

As a molecular biologist, I can't claim expertise in the global warming debate. Nonetheless, as someone trained in the sciences and having a personality with insatiable curiosity, I am naturally interested in what all the controversy is about.

The IPCC stands for Intergovernmental Panel on Climate Change and they issued a preliminary report a few months back about the lastest research on global warming.

The media is highlighting the findings:
1. Scientists release a 21-page report strongly linking humans to climate change
2. Report scientist: Evidence of warming on the planet is unequivocal
3. Scientists predict global temperature increases of 3.2-7.1 degrees F by 2100
4. Sea levels could rise between 7 and 23 inches by the end of the century

As a scientist, I have to ask, show me the data!

Rising Temperatures

There are a number of web pages that discuss global warming (just run a google search and be inundated!). The National Climatic Data Center has a pretty good summary of the key ideas and data.

Humans have been measuring temperatures only in the last 120 years. There is no doubt that temperatures have been on the rise of late.



image source: http://lwf.ncdc.noaa.gov/oa/climate/globtemp.html

Shrinking Arctic ice is another clue that something is happening.



image source: http://lwf.ncdc.noaa.gov/img/climate/globalwarming/ipcc14.gif

However, one might wonder, how does current warming compare with temperatures further in the past?

How does one measure temperatures in days before we had thermometers and weather reports in newspapers?

This web page from the Environmental Protection Agency explains:

Scientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of surrogate, or "proxy," measures of climate such as ice cores, boreholes, tree rings, glacier lengths, pollen remains, and ocean sediments, and by studying changes in the Earth's orbit around the sun.

Image source: http://www.epa.gov/climatechange/science/pastcc.html

As a member of the guild of science, I do have to ask, show me the error bars on the data! How reliable are these "multi-proxy" techniques?

This data does nonetheless suggest that temperatures have been on the rise overall in the last couple of centuries.

However, the last few centuries is but a small snippet of time compared to the age of the earth.

This PBS-WGBH-NOVA page has a good introduction to the earth's history with periodic Ice Ages. If I'm reading Prof. Maasch's (University of Maine, Department of Geological Sciences) correctly, he would attribute three major factors to climate conditions: geographic (distribution of land masses and oceans), astronomical (irregularities in the earth's orbit and solar intensity) and atmospheric (greenhouse gasses).

Since Prof. Maasch is in the geology department, his article dwelt mostly on geographic factors. He also addressed greenhouse gases. He didn't say too much about the astronomical contribution known as the Milankovitch theory.

The orbit of the earth around the sun has cyclical irregularities.

He determined that the earth "wobbles" in its orbit. The earth's "tilt" is what causes seasons, and changes in the tilt of the earth change the strength of the seasons. The seasons can also be accentuated or modified by the eccentricity (degree of roundness) of the orbital path around the sun, and the precession effect, the position of the solstices in the annual orbit.

As a scientist, there is no getting around the data that we are currently in a warming trend. The measurements of the last 120 years is pretty good evidence. Looking further back, the data gets a little sketchier but still looks reasonable.

If I had a climate scientist to talk to, I'd ask the following questions:
How good are the techniques in assessing temperatures prior to historical record keeping?
What do you think are the relative contributions of geologic, astronomic and atmospheric factors to climate?
How does the current warming stack up against other warming trends in our geologic past?

The current concern about global warming is contingent on the belief that the human factor is significant. There is nothing humans can do about geology or astronomy. However, humans may affect the atmosphere through the production of greenhouse gases as a consequence of industrialization.

The Greenhouse Effect



Image source: http://www.koshland-science-museum.org/exhibitgcc/causes02.jsp

Simply put, energy from the sun heats up the earth. Some of that energy bounces back into space but the atmosphere traps some of it. Certain greenhouse gases accomplish this.

Mars, the 4th planet has too little atmosphere to trap much heat thus it is cold. Venus, the 2nd planet has a thick atmosphere and so the heat there is extreme. The Earth, the 3rd planet is just right, enough atmosphere to trap heat to the relatively comfortable world we live in now.

The diagram highlights the greenhouse gases generated by human activity. It notes that carbon dioxides has the biggest contribution to the greenhouse effect. Indeed, with industrialization, atmospheric carbon dioxide has increased dramatically.

However, it should be noted it leaves out an important greenhouse gas which human activity has little impact upon: water vapor!

Question for the climate scientists out there ... how large is the contribution of water vapor compared to the ones we have control over?

Global Energy Balance


image source: http://www.grida.no/climate/ipcc_tar/wg1/041.htm

Whoa! That looks complicated! This energy balance affects the overall global temperature. For instance, if for some reason the influx of energy from the sun were to increase, the balance is shifted. Likewise, an increase in greenhouse gases would cause a shift.

I have to ask, how confident are we about the numbers in this energy balance? What are the "error bars" for each item on the diagram?

My current view is that there is some global warming happening. The data looks pretty good. What I'm less clear on is (1) the scale of the warming and (2) the relative contributions of the different factors in global temperature.

In the meantime, I do strive to conserve energy by shutting off lights and driving a fuel efficient car. I am also looking into changing out my lightbulbs for more efficient ones.

Stay tuned as the scientists and policy-makers continue to analyze the issue and develop recommendations on how to proceed.

UPDATE: The Canada National Post has been running a series of articles from scientists (this item is 27th in the series) who are not sure about global warming.