Perhaps a lot of climate deniers are frustrated by scientists because they think the scientists claim to be know-it-alls. This is far from true. It is true that scientists almost uniformly agree that humans are warming the climate and that they base this conclusion upon “the extreme rate of the 20th century temperature changes and the inability of climate models to simulate such warming without including the role of greenhouse gas pollution.” These are things that climate scientists do know, according to Quirin Schiermeier, author of “The Real Holes in Climate Science,” published in the January 21, 2010 edition of Nature (available online only to subscribers).

What don’t we know? Schiermeier presents four major categories.

The first is “Regional climate prediction rate.” Schiermeier begins the section with this:  “The sad truth of climate science is that the most crucial information is the least reliable.” He indicates that researchers are struggling to develop tools to more accurately forecast regional changes in climate. People are concerned about overall heating of the planet, of course. What they are more concerned about, though is how climate change is going to affect their particular region. Unfortunately, science does not yet have the tools to make precise conclusions regarding regions or countries. This is especially true when “dealing in regions with complex typography, such as where mountains form a wall between two climatically different plains.

Precipitation.  Schiermeier indicates that rising global temperatures “are likely to increase evaporation and accelerate the global hydrological cycle–a change that will drive subtropical areas and increased precipitation at higher latitudes.” Unfortunately, predicting precipitation is extremely difficult, especially winter precipitation. In fact, today’s climate models underestimate how much precipitation has already changed. Scientists are working to improve precipitation prediction by considering additional climate variables, and including high-resolution satellite observations to check their theoretical models.

Aerosols. Schiermeier indicates that airborne liquid and solid particles “are a source of great uncertainty in climate science.” He indicates science must still use “huge error bars when assessing how particles such as sulfates, black carbon, sea salt and dust affects temperature and rainfall.” He indicates that it is widely thought that these aerosols cool climate by blocking sunlight but the models diverge widely. He also indicates that the lack of data hinders this research in that scientists have difficulty knowing what is actually in the air. To complicate things, black carbon tends to absorb sunlight, which warms the planet and probably inhibits rainfall. Sulfates, on the other hand, exert a cooling influence, but determining the net effect is complicated.”

The relationship between aerosols and clouds further complicates the situation. Before a cloud can produce rain or snow, rain drops or ice particles must form and aerosols often serve as the nuclei for condensation. But although some aerosols enhance cloudiness, others seem to reduce it. Aerosols could also have a tremendous impact on temperatures altering the formation and lifetime of low-level clouds, which reflect sunlight and cool the planet’s surface.

The tree ring controversy. Schiermeier indicates that temperature measurements over the past 150-years show “a sharp temperature rise during recent decades that cannot be explained by any natural pattern. It is most likely to have been caused by anthropogenic greenhouse-gas emissions.”  But reliable thermometer records from before 1850 are scarce and researchers must find other ways to reveal earlier temperature trends. One of these sources of information has been tree ring measurements, but there are others. “As trees grow, . . . . they develop annual rings whose thickness reflux temperature and rainfall. Proxies such as these provide most knowledge of the past climate fluctuations . . . ”

Other sources of proxy data include coral reefs, lake sediments and glacial movements and historical accounts. When these proxy records are “stitched together” they resemble a “hockey stick” pattern, with temperatures rising rapidly during the late 20th century. Schiermeier indicates, however, that using and interpreting these “proxy records” has generated considerable controversy. Some scientists continue to raise legitimate questions about these “paleoclimate proxies.”

Schiermeier indicates that even with questions regarding the proxy data, it is still the case that most mid-20th-century warming is “very likely” due to human caused increases in greenhouse-gas concentration. This conclusion was based upon far more than one line of data.

Perhaps it would be to the advantage of scientists to clearly disclose what they don’t know when they do announce their conclusions.  Or, actually, having written this, I now wonder whether the problem is with our news media which tends to oversimplify the findings of climate scientists (and all other scientists). That could be analyzed rather simply, it would seem, but comparing the media reports of the next big climate finding that is widely reported in the media with the actual writings of the scientists.

Regardless of blame, it seems that presenting a balanced presentation of what the data strongly shows versus the questions that remain unanswered might calm some of the climate change deniers.