Breaking Down Weather and Climate Extremes

Several Factors Required for Attribution to Extremes

Any weather phenomenon can impact any location on Earth at any time, but the probability of occurrence of each event varies. As the global population increases and expands, more weather events are being reported locally. This fact alone may lead to more extreme weather events being observed. Global climatic changes may influence the actual number of extreme weather event occurrences. Long term variability in atmospheric circulations may be linked to natural or anthropogenic (human influenced) effects. There are likely atmospheric impacts from both scenarios.

Source: NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds).

Regional Variability in the Earth's Atmosphere

Without weather, seasonal changes would not happen. All else being equal, your climate would remain stagnant and boring. Interactions between regions of different climates and their land, sea, and air interfaces drive local weather patterns. To complicate things more, different elevations exist among these boundaries. Vast mountain ranges and valleys extend across multiple continental borders. Underwater canyons and ridges spread out across all ocean basins. Atmospheric waves can affect the heights of temperature, pressure, moisture, etc. In addition, particulate matter interacts chemically, biologically, geologically, and physically as particles are transported around the world.

Observed Precipitation Changes

Source: Figure SPM.2 from the IPCC 5th Assessment Report Working Group 1

Super-saturating a Warmer Atmosphere

Climate scientists have shown that as global atmospheric temperatures rise due at least in part to human activities, water vapor concentrations will also rise. In terms of thermodynamics, a single water vapor molecule has a higher heat capacity than that of dry air. This means that water vapor molecules have the ability to hold more moisture at higher temperatures. Oceans cover approximately 70% of the Earth's surface area. As sea surface temperatures rise, evaporation rates into the atmosphere increase the water vapor content in the atmosphere. Having the greater quantity of moisture in the warmer atmosphere would allow clouds to hold moisture longer before producing precipitation. Timing between each weather event lengthens while clouds take longer to condense. This results in both shorter-lived intense precipitation events and longer-term droughts.

New Jersey Flooding from Hurricane Sandy

Source: Wikimedia Commons

Increased Vulnerability from Human Migrations

Populations have increasingly been relocating towards coastal areas. These migrations increase their vulnerability to being impacted from coastal storms. Flooding from storm surges has the highest impacts along coastlines. This is true with or without any statistical long term trends in storm frequency or intensity. Any location can be impacted from extreme events, but coastal residents should especially be aware of their increased vulnerability.