I ran across an interesting map on the National Climate Data Center website that makes me question how much global warming has affected us here in Georgia. The map, shown below, plots the annual mean temperature trend in the state from 1985 through 2006:

It’s fairly obvious that the mean temperature has actually been decreasing over the past 112 years, by .06 degrees per decade. You can see that the stage has alternated between periods of relatively warm and relatively cool weather, with a colder than normal spell from the mid 50s through the early 80s, and a warmer than normal period from the early 80s on.

Of course, for many people alive today, that trend would cause us to think that it’s gotten warmer since childhood, hence the belief that we must be having global warming. Few people remember the warm temperatures recorded during the period from 1910 through 1935, when it was warmer than it is today. The warmest year recorded was back in 1923.

You can go to this page to create your own chart, or a table of mean temperatures.

The Climactic Data Center of the National Weather Service has now declared 2006 to be the warmest year on record, based on preliminary temperature data for the entire year. In December, they estimated that the year would go down as the third warmest, but the warm spell during the second half of the month increased the average enough to break the 111 year record.

The national average was 55 degrees, 2.2 degrees above the 20th century average, and a measly 0.07 degrees above the previous record, set in 1998. In fact, using a new methodology for temperature measurement that will go into effect this year, 1998 remains the warmest year.

New Jersey experienced its warmest temperatures ever in 2006, and much of the Northeast, Midwest, and Plains states had top five warmest years. The Southeast and West Coast were also warmer than normal, although not nearly as much as the rest of the country. No state experienced below normal temperatures last year.

So, is this evidence of global warming? The Weather Service hedges the point, saying, “It is unclear how much of the recent anomalous warmth was due to greenhouse-gas-induced warming and how much was due to the El Niño-related circulation pattern. It is known that El Niño is playing a major role in this winter’s short-term warm period.”

On the precipitation side, things were nowhere near as extreme. Only Georgia, Florida, Wyoming, and North Dakota experience much below normal rainfall, while parts of New England and the Midwest had much above normal precipitation. No state set a precipitation record, either dry or wet for the year.

You can read the entire report here.

The spell of hot weather we’ve seen for the last ten days is winding down. A trough split is likely to bring cooler weather to Georgia through the end of the month, with high temperatures below 90 degrees. Even better, we are likely to see some rainfall during the period, unfortunately most likely this weekend and next weekend, but with less than 20% of normal rainfall for July, who’s complaining.

While the lack of rain exacerbated the effects of the warm weather, we were nowhere near record breaking temperatures, which are typically the hottest of the year for the third week of July. The high temperature this week was 96 in Atlanta, and 97 here, however the records for the week are all in the 100s, including the 105 degree all time high temperature in Atlanta, set on both July 13th and July 17th, 1980. (From July 6th through 17th, 1980 holds the record high temperature six times. I remember that year — it was one month after I moved to Georgia, and I wondered what I was getting into). Still, we’re averaging about 1 degree above normal July temperatures.

Other parts of the country have seen plenty of records fall, though, particularly in the upper Midwest and Plains states. Even Europe is getting into the act — England recorded its warmest temperature ever this week, and you can see the parched course at the British Open on TV.

Tropical Storm Beryl is getting ready to hit the Northeast with more rain. While bringing relief from the heat, that part of the country is the one area that doesn’t need any more precipitation.

Looking beyond the end of the month, the heat is likely to return in August to many of the same places we saw it for most of July. The Climate Prediction Center just released its preliminary forecast for August, and on the temperature side, it largely matches the forecast for this month, except for the Carolinas, where normal rather than warmer than normal temperatures will be seen. Look for normal precipitation for August, which will likely be an increase over what we saw this month.

The week of July 16th will have much of the United States in the frying pan, with some of the warmest temperatures of the summer. Highs in the upper 90s are expected for most of the country, as the below map of Tuesday’s predicted highs show:

Just to give you some idea, here are Tuesday’s predicted high temperatures, along with normal highs for mid-July:

Boise, Idaho: 97, Normal is 89
Cleveland, Ohio: 91, Normal is 82.
Lawrenceville, Georgia: 95, Normal is 88.
Little Rock, Arkansas: 100, Normal is 93
Missoula, Montana: 90, Normal is 84.
Montpelier, Vermont: 91, Normal is 78.
Omaha, Nebraska: 100, Normal is 88.
State College, Pennsylvania 95, normal is 81.
Tusla, Oklahoma: 102, Normal is 94.

You can expect to see a number of heat advisories nationwide this week.

The good news is, at least for Georgia, is that the models are advertising a cool down for the week of the 24th, with highs in the mid 80s, and a greater chance of rain than normal. We can only hope.

The weather in June, 2006 will be remembered for a lack of rain in many places, and an overabundance in others.

In North Georgia, the average temperature for June ended up at 77.2 degrees, or about 0.3 degrees warmer than normal. In Athens, the average was 77.4, or about 1.1 degrees warmer than normal. Athens also recorded a record 102 degree high temperature on June 22nd, one of two days when the thermometer broke the century mark. However, here in Lawrenceville, I only recorded an average of 75.6 degrees, or between a degree and a degree and a half cooler than expected.

Rainfall, as is typical for summer thunderstorms, was very dependent on location. Atlanta had 160% of normal rain with 5.8 inches of rain, most of which was recorded during the last weekend of the month. However, Athens had a shortage, with only 1.97 degrees, or 50% of normal, and my rain gauge in Lawrenceville recorded 1.99 inches of rainfall.

The big weather story for the month was in the Northeast, as what seemed like never-ending rain caused flooding and evacuations. In Boston, 10.09 inches of rain marked the third wettest June ever. Combined with 12.48 inches of rain in May, it was the wettest May-June period on record. The torrential rains also affected much of the mid Atlantic states, with flooding in Pennsylvania, Maryland, and New Jersey.

Also notable in the Atlanta area was the relative lack of humidity. We enjoyed a mean humidity of 65%–so far the lowest humidity month of the year. Compare that with an average of 78% in June, 2005, and 85% in June, 2004, and you can see it ended up being much dryer. Part of the reason for this was the relatively few number of rain days, but part can be credited to the bad weather in the Northeast, which led to a general northwesterly flow of air, as opposed to the more typical southeasterly flow, bringing humidity from the Gulf of Mexico.

What can you expect in July? The hot weather we’ve seen over the last few days will continue through midweek, when increasing humidity will lead to a chance of thunderstorms. After that, the long-promised trough along the eastern seaboard is likely to bring a wet, cooler than average period around the middle of the month. The weather service is still predicting a Georgia July with above normal temperatures, and equal chances of above-normal or below-normal precipitation.

One final note: On Wednesday, the sun begins to set earlier in the day, at 8:50 PM, instead of 8:51, where it has been stuck since back on June 23rd. It started getting light later back on June 16th, albeit very slowly - sunrise is only two minutes later than it was then. Things will start to accelerate, though. By the end of July, we will have lost half an hour of daylight.