Extreme Weather

Everyday weather, in contrast to extreme weather, is a natural occurrence in the lower atmosphere (troposphere) of the earth. Sunshine warms the earth unevenly since land and water absorb energy differently. In addition there is uneven topography in the forms of mountains, valleys, and hills which lead to further unequal heating. The earth axis is tilted 23.5 degrees - that combined with the orbital shape leads to the seasons.

What Is Normal Anyway?

But as far as day-to-day weather it is important to note that the angle of solar radiation impinging on the surface is at a much greater angle in poleward locations versus near the equator. If this isn't enough the earth spins on its axis, one revolution per 24 hours. As a result of the above effects - the atmosphere is constantly attempting to reach equilibrium, as hotter air flows poleward, colder air flows equator-ward, air flows from high pressure toward low pressure. Air masses collide or air is driven upwards and downwards in this effort to reach some equilibrium. As air is pushed upward it cools, condenses, and clouds form, which can lead to precipitation. As air sinks it warms and dries out. Air masses collide in the horizontal of course; cold air advances over taking warmer air (cold fronts) and warmer air pushes poleward (warm fronts).

One could say there really isn't "normal" weather, but possibly the averaging of extreme weather. But scientists attempt to describe "average" weather (typically the last 30 years of data at a surface weather station). However atmospheric scientists can describe how conditions have changed since records began and how they have been deviating from observations within the period of climate average or entire climate record. One of the more obvious impacts due to climate change and global warming are hotter temperatures which will lead to more frequent and intense heatwaves across many parts of the globe. The number of heatwaves (defined as 3 or more days in a row of 90 degrees or greater, in the northern hemisphere) is expected to increase by around 25% in Chicago by the end of this century, for example. Model results show an expected 3 days added to the typical heatwave of the late 21st century.

photo from images.travelpod.com

Hurricanes are expected to increase in number and severity with the expected warming of the oceans. The warm ocean water serves as the heat pump engine for these storms and as the water temperature goes up, so does the source of this energy. Modelling results from various studies indicate that the intensity of tropical cyclones will increase, along with rainfall rates. The number of intense hurricanes (i.e., category 4-5) will increase substantially leading to more extreme weather, while the overall number of systems per year should remain relatively unchanged. Still some experts expect that Very active hurricane seasons, such as the one in 2005, would become the norm versus an anomaly.

Longer Term Effects

Finally, with more extreme weather will come an increase in the severity of both flooding storms and drought conditions. Unfortunately areas that are already prone to drought are expected to get more severe and longer lasting droughts. The warmer atmosphere will lead to an increase in the capacity of the atmosphere to hold moisture and will lead to more frequent heavy precipitation events.

The frequency of extreme weather will probably get worse over time.

The effects of climate change will continue to be felt far and wide.

To notice these subtle and not-so-subtle effects are key if we are to survive climate change.