The Weather Guys

A barely colder than normal May has been followed by an extremely warm and dry first two weeks of June.

Through Friday June 11th, Madison had five days with high temperatures above 90 degrees, and the month has thus far averaged more than 11 degrees above normal.

Simultaneously, the dry spring has continued into the early summer with the month of June already 1.69 inches of rain below normal, and that’s after April and May came in at a combined 4.24 inches below normal.

Coincidentally, this week the National Oceanic and Atmospheric Administration (NOAA) reported that the monthly average carbon dioxide (CO2) fraction in the atmosphere, as measured at the top of Mauna Loa in Hawaii, set a new record of 418.92 ppm (parts per million) in May.

This represents a larger than 50% increase in atmospheric CO2 concentration since the pre-industrial age (1750-1800), when the value was about 280 ppm as measured by analysis of air bubbles in ice cores taken from ice sheets in Antarctica and Greenland. The current value has not been observed on Earth in the last 4.1 million to 4.5 million years, when sea levels were 78 feet higher than they are today and the global average temperature was 7 degrees warmer than at present.

Not even the COVID-19 pandemic was able to put a dent in the rate of increase in CO2, which suggests that, unless we change the nature of our energy use, we are continuing to forge a path toward a very different, and likely extremely adverse, climate future.

Since solar and wind energies are already cheaper than fossil fuels and they work at the scales necessary to power the world, there is no reasonable excuse for not moving aggressively to a more sustainable energy future.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.

Evidence of the presence of water in our atmosphere is ubiquitous.

Water occurs in the Earth’s atmosphere in all three of its phases — solid (snow and ice), liquid (rain and dew) and gas (invisible water vapor). As we begin to emerge from the recent cool spell and really enter spring/summer, we may begin to see more dew on the ground and on the windshields of cars in the morning.

The air nearly always holds some amount of water vapor. Dew is liquid water that condenses overnight onto objects when the air that contains the water vapor cools to a sufficiently low temperature.

One of the important and microscopic characteristics of the condensation process is that water vapor will not condense into liquid water very easily unless it condenses onto a foreign object such as the tiny hairlike structures on grasses or dust and pollen particles on windshields. In fact, on particularly dewy mornings, if you wait for the dew to evaporate you may find yellow stains on your windshield that are left as the liquid water evaporates, leaving the pollen particles on which it originally condensed.

The formation of raindrops requires a similar collection of foreign objects upon which water vapor can condense. Such objects are known as cloud condensation nuclei, and a great number of naturally occurring substances can serve this role, including dust particles, smoke particles, salt particles, pollen grains, particulate matter from smokestacks, and naturally occurring aerosol particles.

Without these cloud condensation nuclei, the formation of cloud liquid water droplets, and eventually precipitation-sized particles (which are 1 million times more voluminous), would be considerably more difficult in our atmosphere.

In that case, rain and snow would be rare occurrences and life on the planet would be put at risk.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.