Published Tuesday, April 10,  2001 in the San Jose Mercury News


A warm day outside can be hazardous inside car

Sunny days in the Bay Area are often relatively mild -- unless you are inside an enclosed automobile. In recent experiments this spring, I found that the combination of a warm day and an enclosed car can quickly convert a pleasant outside temperature into a dangerous vehicular scorcher, with thermometer readings high enough to cause serious health problems.

Studies by the Louisiana State Medical Society in 1995 found that on a day when the outside air temperature was 93 degrees, the temperature inside a parked car rose to about 125 degrees after 20 minutes and stabilized at 138 degrees after 40 minutes. Their experiment looked at both light- and dark-colored vehicles, cars parked in direct sun and shade and cars with completely sealed windows and windows open slightly.

To see what the results might be in our more temperate climate, I recently conducted a similar experiment on a relatively mild day in Fremont when the outside air temperature was only 72 degrees. The air temperature inside a blue Honda Accord with a medium-gray interior, but not parked in direct sunlight, rose to 98.5 degrees after 10 minutes and to 103.4 after 20 minutes. Readings in the direct sun were about 10 degrees warmer!

Medical experts say those most at risk of illness or death from such high temperatures are children and the elderly, whose bodies are less efficient at regulating temperature. When a person's temperature hits 106 degrees, the risk of permanent brain damage rapidly increases, and death can result quickly. Also at risk are pets.

As these figures show, even a short amount of time in an enclosed car can be extremely dangerous. The bottom line is that people and pets should not be left in uncooled, enclosed cars.

Is there a packaged system that measures AQI? Are they expensive? I would like to measure AQI for candidate-retirement locations, and the data is not published for many of the locations I'm interested in. What is the most significant component to the AQI that I should be concerned about from a personal health and comfort perspective? How easily and cheaply can I measure that component?  John Arnold - Saratoga

First, here is some background for the ``AQI challenged.'' AQI is Air Quality Index, recently established by the Environmental Protection Agency for the five major air pollutants regulated by the Clean Air Act. These are ground-level ozone, particulate matter such as soot, carbon monoxide, sulfur dioxide and nitrogen dioxide. The index uses a scale from 0 to 500, in which values of more than 100 in any category are considered unhealthy. While some individuals may be more susceptible to different pollutants than others, the index serves as a good set of guidelines for most of the population. To find out more about the AQI see

The actual measurement of these pollutants takes very sophisticated and very expensive equipment. Even if you were to obtain such equipment, it would give you a snapshot of the current conditions only on the particular day that you were sampling. In finding a suitable retirement location, you'd want to find out the historical occurrence of unhealthy conditions and evaluate whether they exceeded what you might be comfortable with. In larger urban areas and their surrounding environs, the local air pollution control district takes these measurements and determines how often they occur. In smaller cities and towns, this task generally falls upon the state air resources board or equivalent agency. These agencies should be contacted for the areas in which you have an interest.

Apparently, NASA has found a way in which Earth releases excess warmth through clouds over the Pacific Ocean, according to information at My prediction is that within a few years, the global warming myth will be debunked. The same is true for the ozone depletion. Both have more to do with natural causes such as sun activity than with anything man can do short of a nuclear war. The real cause of these myths is political, not scientific. What do you think?  Joe Nardini - Fremont

From a scientific point of view, this finding further reinforces the fact that we're still learning about our planet and its atmosphere, and that there are still many more questions than answers. However, from all of the evidence I have seen, global warming is real. The important questions that I have not seen satisfactorily answered relate to the magnitude of the warming, length of time, the reason for the warming and what its impacts will be. For example, how much of the warming is from natural variation and how much is the result of human activities?

And the debate becomes further muddled when such a complicated scientific problem becomes embroiled in partisan politics. Under the Clinton administration, the United States became a signatory to the Kyoto Protocol, which seeks to limit the emission of greenhouse gases by nations of the world. Now the current administration is removing the United States as a participant without any significant scientific breakthroughs as justification. Consequently, we not only have to figure out an incredibly complex scientific problem but also have to factor in which political party is in power.

Correction: In my comments about the recent warmth during March, I mistakenly cited San Jose's average March temperature at 67 degrees, when it is actually 65.Additionally, there have not been any March records above 90 degrees, as I cited from a National Weather Service document. Thanks to Dexter Hermstad of Saratoga for finding these errors.

Jan Null, founder of Golden Gate Weather Services, is a retired lead forecaster with the National Weather Service.  Send questions to him c/o WeatherCorner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif. 95190. You also can telephone questions at (510) 657-2246, fax them to (510) 315-3015 or e-mail them to Please indicate in your e-mail what city you live in.