Sep. 2, 2017

Update on Extreme Weather

This Harvey flood event is on an entirely different scale than what we’ve ever seen before in the history of the United States. The storm has unloaded over 50 inches of rain east of Houston, the greatest amount ever recorded in the Lower 48 states from a single storm. This is an extreme weather event and there are similar floods across the globe ongoing. In this week alone, 2/3rds of Bangladesh is now underwater due to flash flooding. 1200 are dead in Bombay and Nepal flash floods. MILLIONS are now homeless there. 100,000 people fled their homes due to massive flooding in Nigeria. All this is happening right now. An increase in the intensity and precipitation of storms was predicted back in the 1980's. It appears these predictions are accurate.

Yes, I have been keeping up with the research for three decades. I became aware of global warming while earning my Bachelor of Science degree in Earth Sciences back in 1985. As a matter of fact, you can’t pick up any popular science magazine without finding some article reviewing research on climate change or acidification of the oceans. And in terms of academic research publication, there are tens of thousands of studies in so many different fields of science. There is a preponderance and convergence of evidence supporting concerns about anthropogenic climate change.

On the other extreme, a wildfire on the northwest edge of Los Angeles spread rapidly on Saturday despite light rainfall, a day after it forced the evacuation of hundreds of residents and triggered the closure of a major highway. Wildfires in the U.S. West have burned more than 7.1 million acres (2.9 million hectares) since the beginning of the year, about 50 percent more than during the same time period in 2016, according to the National Interagency Fire Center. So, these weather events related to climate change are not just flooding, or high winds or drought- it’s all of it. Excess heat in the atmosphere amplifies whatever weather is already trending in a region.

So climate change isn’t the reason we got hit by Harvey, but excess heat in the atmosphere is certainly related to the incredible amount of rain that was dumped on S. Texas and Louisiana. It is a fact that warmer air can hold more moisture and warm ocean waters give energy to storms.

Let me also say that one result of scientific illiteracy is that people will accept simplified explanations for complex situations. For example someone who lacks full understanding of the complexity of global warming might argue, “But it snowed up north last winter.” One needs to study these things to gain a full grasp because it’s really complex.  

So, let’s address issues with the polar vortex and extreme snow events. The higher latitudes seemed to be more vulnerable to climate change and temperature variations seem to be greater there. Cold, dry air creates high pressure systems, but as the Arctic warms it can no longer hold the high pressure system and the jet stream dips down bringing polar air further south. The net result has been to increase delivery of cold air into parts of Eurasia and North America, particularly in late winter and early spring. It’s counterintuitive, but when the polar vortex is weak, it’s more unstable, and cold air outbreaks from the Arctic southward toward the mid-latitudes become more likely. (When it’s strong, the cold air is more contained in the Arctic and the mid-latitudes are milder.) So extreme precipitation, be that water or snow is the result of increasing temperatures.

 Harvey was pinched between two high pressure domes, which is why it moved so slowly and dumped so much more rain in a localized area. Here is a link that explains how warmer global temperatures affect high and low pressure systems. It is a synopsis of a paper called: Quasiresonant Amplification of Planetary Waves and Recent Northern Hemispheric Weather Extremes.