In my previous Climate Blue column, I started a framework for those who want to think, seriously, about how climate change will affect their life, their community, or their business. The framework pushes one to confront the complexities and contradictions inherent in climate science. And it reveals that some of those contradictions are not contradictions at all.The path started with a warming Earth, then considered whether this would produce more or less precipitation. The answer to the precipitation question was conditional: Is water available from the surface, lakes, oceans, or soil, to supply the atmosphere? And is the precipitation frozen or not? These conditions, wet or dry and above or below freezing, are sources of complexity.
In a place that regularly and historically experiences both wet and dry weather patterns, each outcome — sometimes wetter and sometimes drier — is expected. A distinction was made between the intensity of the precipitation (rains harder, snows more) and the accumulation of water in a particular place. We expect and already experience more intense precipitation when it does rain.
Those adapting to climate change also should be aware of the changing characteristics of storms. As conditions become wetter or drier, different impacts and challenges will arise.
The acute phase: Weather
When we think of storms and the damage they cause, it’s likely that thunderstorms, tornadoes, and hurricanes come to mind. Whether or not a particular type of storm is “becoming more intense” is one of the most controversial and useless points of public argument, and it is not the subject of this article.
Think of storms as a collection of those things we use to define weather: temperature, precipitation, and wind. In a warming climate, storms have to change; basically, we are adding more energy to them. And when additional water is available (via lakes, oceans, soil), storms are likely to have more intense precipitation, which often leads to flooding.
The storm can, however, accommodate the extra energy in many ways. It could have stronger winds or larger amounts of precipitation. It could be spread over a larger area.
Most planners concerned about their home surviving a severe storm consider wind damage first (a roof, perhaps), followed by intense precipitation and flooding. Intense heat and cold bring focus to the ability to cool or heat the house. All of these challenges represent the acute phase, the immediate, instantaneous effects of weather. Most of us are knowledgeable of these weather risks. It’s reasonable to consider that a warming world will change our approaches to managing this risk incrementally.
It is easy to equate the immediate damage to your home with the damage to entire communities or businesses. It is also easy to imagine that a community’s decisions regarding stormwater management and infrastructure maintenance influence what happens to individual homes and businesses.
One challenge of a warming climate is that the design and construction decisions affecting existing buildings were made in a climate that is different from today’s. The standards on the books are outdated. Even if we apply current climate observations to the future, we know they will not be appropriate 50 years from now.
The chronic phase: Climate, perhaps
The accumulation of heat is at the core of planetary warming. We are heating the ocean and melting ice. The accumulation of heat has a large influence on whether it will get wetter or drier.
One way to think about accumulated effects is to walk through the seasons of a year. Since most readers of this column have spent some time in Ann Arbor, Mich., I will use it as an example. This walk is relevant, however, to large parts of the U.S.
In a Michigan summer, much of the rain comes in thunderstorms. We have already observed that it is raining harder, which might be measured in inches per hour.
But is it raining more?
One consequence of more rain is wetter soil that can no longer absorb water. Therefore, smaller amounts of rain cause flooding, and the flooding occurs more quickly. The wet soil loosens tree roots, which are more easily blown over. An increase of wind is not even required to cause more tree damage. More toppled trees wreak havoc on homes and power lines. Runoff into lakes and rivers raises their levels and lowers water quality. Water tables rise as aquifers fill up. We’re left with a condition of chronic flooding.
Now consider the winter. The fall, winter, and spring storms contain abundant moisture, and there has been both more rain and more intense rain. When it is cold enough to snow, the accumulation can be deep. The snow is likely wet and near the freezing point.
One of the most prominent signals of our warming climate is that winter is getting warmer faster than other seasons. There is more rain in winter and more rain on snow, leading to melting. The ground is saturated. Midwinter, which was frozen 30 years ago, is more likely to be muddy. Runoff into the streams and lakes happens earlier in the spring, perhaps even in late winter. There is more of a burst of spring runoff than a steady stream. The seasonal cycle of water is changed, with consequences throughout the year.
Ann Arbor, like much of the Great Lakes region and the Northeast U.S., has been experiencing persistent, wet conditions. It is a region, though, that has also had a history of dry periods and drought. When the pattern shifts to supporting drought, the temperature is warmer, and the onset of drought is likely more sudden. This is an emerging phenomenon called flash drought.
What to do? What to do?
The goal, here, is to expose that when planning, it is useful to think about whether the direct and immediate effects of storms are important, or whether we should focus on the accumulated effects of more or less moisture.
In many cases, each matters but in different ways. It is important to target the analysis to the particular type of problem you are trying to address.
I have maintained, in many articles, that humans have experience managing storms and wet and dry periods. Hence, what we need to do, first, is manage these stormier, wetter, and drier conditions. Less intuitive is that all of these conditions are continuing to change, and it may not be reasonable to address these challenges with incremental alterations to our old methods.
We also need to consider a more difficult situation: If we do not intervene and cap the increasing temperature, when do we abandon incremental approaches?
In my next column, I will develop a plausible storyline to think about wildfires, which brings biology — and even more complexity — into the framework.
(The lead image is the author in a kayak during Hurricane Isabel, Cape Anne, Md. )