Wild Weather Across the Globe: What's to Blame?

(Aug 7) -- Intense heat waves are pounding the United States and Russia (among other parts of the globe). The monsoon is producing horrendous flooding in Pakistan -- and even the parts of India where rain is rare. Argentina and southern Brazil are experiencing unusual amounts of winter snow and cold.

Global warming is often blamed for all weather extremes. This year, with the extreme weather including more than a dozen nations experiencing all-time record-breaking warmth, it's understandable -- and may very well be a contributor -- but La Nina may be more responsible for these short-term weather events.

Global warming is not a progressive, non-stop march toward hotter weather, with each summer hotter than the last and each winter less cold than the previous. Global warming cannot be refuted by a year of widespread record cold or proven by a year of widespread record warmth. The data needed to draw conclusions related to climate change needs to be collected (estimated for years prior to when accurate weather records were kept) for decades and even centuries.

The amount of data from this northern hemisphere summer -- even though supportive in terms of warmth -- is a minuscule amount of data, and a small amount of data cannot prove or disprove any hypothesis in science.

That's not to say that global warming might not be a factor.

June marked the 304th consecutive month with a global temperature above the 20th century average, according to National Oceanic and Atmospheric Administration (NOAA). A hot summer weather pattern, not necessarily much different than other hot summers, may have been pushed to record levels by adding the cumulative effect of global warming.

It's most likely not that simple, though.

Weather is created by a combination of many factors (not all have been identified or completely understood), including multi-decade sea surface temperature cycles, changes in ocean currents, fluctuations in upper-level patterns, the amount of volcanic ash in the atmosphere and even the amount of incoming energy from the sun are some.

Dramatic weather events are much more likely to be attributable to other well-known weather factors, such as El Nino or La Nina, than global warming. The cause-and-effect relationship of these can be measured a period of months rather than decades or centuries.


(Image courtesy of NOAA)

A La Nina occurs when sea surface temperatures in the equatorial Pacific are cooler than normal, and cooler water over a significant portion of the largest ocean in the world affects the weather world-wide. An El Nino, in contrast, is when sea surface temperatures in the same region are warmer than normal.

The current La Nina, one that's been developing for the past couple of months, may be contributing to some of the recent weather extremes. It's not uncommon for severe cold and snow to occur in Argentina and southern Brazil in years with a La Nina, and wetter-than-normal monsoon seasons in the Indian ocean are also associated with a La Nina.

As far as the United States is concerned, the most well-known effects of a La Nina occur during the winter, not during the summer, but it is believed to be a contributing factor in active hurricane seasons as was indicated in a NOAA press release this week. Patterns conducive to hurricane formation are often associated with a strong upper-level high pressure systems over the western Atlantic and eastern half of the United States. This is the same type of high pressure system that's been creating the intense southern -- and occasional Mid-Atlantic and Northeastern heat -- this summer.