Travelers to Washington, D.C.'s famous National Cherry Blossom Festival may be disappointed this year due to the exceedingly warm climate in the D.C. area and across most of the continental United States, in which late winter temperatures have been running 20 to more than 40 degrees F above normal.

Cherry blossoms at or near peak bloom in Washington, D.C.'s Tidal Basin, March 18, 2012. Photo: Michael Halpern

The festival is scheduled to run from March 20 to April 27, but the trees are expected to reach peak bloom in the next day or two, and the blossoms may be off the trees entirely by the time most tourists are normally expected to arrive. Peak bloom is defined as the day on which 70 percent of the blossoms of the Yoshino cherry trees that surround the Tidal Basin are open. This date varies from year to year but the average is April 4.

The official Blooming Period begins when 20 percent of the blossoms are open and lasts until the petals fall and leaves appear. It starts several days before peak bloom and lasts for up to 14 days, so it's likely that the blossoms will all be off the trees by the end of March.

One of the common problems for people not trained in science is that scientific information is not concrete and clear to the senses. Scientists see their data and it's a concrete thing for them, but lacking that direct experience, the general public comes to regard many abstract scientific conclusions derived from that data as matters of belief. This is why ideas persist, for example, that cell phones might cause brain cancer, even though microwaves have 1 millionth the energy needed to ionize a carbon atom and damage DNA -- less even than our skin produces in the form of infrared radiation. That's what Einstein won his Nobel Prize showing, but it's still meaningless to most people until you show them concretely. For example, which would you rather be hit by at 30 mph: a pea, at a mass of 1.4 grams, or a BMW Z4 at 1,395 kg, or about a million times more massive? The answer is obvious. But since a BMW can hurt you if it hits you, does that make all mass suspect? Should we warn people about the grave hazards posed by pea shooters?

The same thing happens with climate change. The data are overwhelming that human behavior is causing the climate to warm, so it's reasonable to suggest that the answer likely lies in changing human behavior. These data are not guesses so much as they are measurements, using instruments called thermometers and the like. There are now literally billions of data points indicating these conclusions, accumulated by thousands of scientists working over five decades. But unless it's made concrete, it's difficult for people to grasp that it is real, and it is easy to become confused.

The extremely early blooming of the cherry blossoms in Washington is one such concretizing event. Another is this weather map showing high temperatures for March 18, 2012:

The United States has set over 2,000 weather records so far this year. In my home state of Minnesota, it was 80°F today. In the "nation's icebox," International Falls, in the northernmost tip of the state, the temperature was 79°F, a whopping 43° above the average high temperature for the date. It was the city's hottest March temperature on record by 6°, but what was even more amazing is that it beat the previous record for the date by a full 13°! The US heat wave is now classed as a 4-sigma event, and one of the most extreme meteorological events in US history.

Visitors enjoy near peak bloom in Washington, D.C.'s Tidal Basin, March 18, 2012. Photo: Michael Halpern

The National Weather Service has now issued a statement that

It is extraordinarily rare for climate locations with 100+ year long periods of records to break records day after day after day... though it is very difficult to precisely quantify just how rare it is because as the period of record grows the likelihood of seeing so many consecutive record-breaking days decreases.

It's important to note, though, that despite all this, weather is not climate. Climate is the statistical average of weather and is determined by broader factors than individual weather incidents -- even extreme ones like this heat wave. So this suggests we should see if we can find more data to show whether or not the current heat wave is a part of natural climate variability.

It turns out we can, by counting the daily record high temperatures and comparing them to the daily record-low temperatures. Because climatology is about averages, we would expect that if the climate were not warming, this ratio would be about even. Some record-highs, and about the same number of record-lows. But a 2009 study showed that daily record-high temperatures have been outpacing daily record-lows by about a 2-to-1 average for the last decade, and just slightly less than this amount during the prior decade. In fact, the trend appears to be continually widening as a chart at the link shows. This trend is inconsistent with with natural variability. Other studies have shown that climate change increases the likelihood of extreme heat events like the one we are currently experiencing.

When taken as a whole this weather pattern is also consistent with what climate scientists have been talking about for the last five decades. As we increase the level of carbon dioxide in the atmosphere, it traps more heat. A warmer atmosphere absorbs more water, which in turn heats the atmosphere even more. More water in the atmosphere means less on earth, so we tend to have more drought. It also means that the atmosphere is more energetic, and that extra energy comes out in more intense storms. So we expect more intense hurricanes and tornadoes. It also means that when it does rain, because there is more water in the atmosphere, it rains (or snows) harder. This is not unlike the recent tornadoes in Michigan and record snowfall in Anchorage. But harder rains fall faster than the ground can absorb them, so you'd expect more runoff. That means more flooding, and it means more fresh water being lost into the oceans, which because of that and absorbed carbon dioxide, are becoming more acidic.

These expected trends are consistent with what the insurance industry has been reporting. Consider this graphic from Munich Re, a major reinsurer of US property and casualty companies:

What's interesting is that while categories of loss not related to the climate have stayed relatively constant, categories related to the climate have quadrupled in the last 30 years.

So the question is, on this balmy 80°F late winter Minnesota day, whether the cherry blossoms in D.C., or the heat waves in the red states, or the melting nation's icebox, will be enough warmth to melt the stone cold hearts in Congress just enough to begin to consider the possibility that they have a responsibility to be basing public policy decisions on the evidence of science instead of the most loudly voiced opinions, or whether it's not yet concrete enough for them. I'm betting the latter.