Part A: Wild Weather and Climate Variability
Source: NCAR image library.
NOAA Makes It Official: 2011 Among Most Extreme Weather Years in History
"Near the halfway point, 2011 has already seen eight weather-related disasters in the U.S. that caused more than $1 billion in damages..." (Source: Scientific American, June 17, 2011). Examples include: heavy snow in the Mid-Atlantic, tornadoes in New England, hurricanes in New York City, record floods in the Midwest and Northeast, and droughts and heatwaves in Texas and the Southwest. Scientists and citizens both wonder: What is causing the wild weatheris it climate change or just an unusual year? It is too early to reach a conclusion, but the question is a hot topic everywhere. In this lab, you will look into the relationship between the recent weather patterns, climate variability, and the changes in Earth's heat content.
Begin by watching the State of the Climate 2009 video from NOAA (1:54 minutes) and answer the Checking In questions below.
Courtesy of StormCenter Communications and NOAA Climate Portal
- How have the past three decades compared to the average temperature on Earth for the past 100 years? The last 3 decades have been warmer than each of the previous. This is unprecedented in the climate record for the past 100-150 years.
- As the ocean gains heat, what happens to the humidity levels in the air? How might this change weather events? The warmer the ocean, the more humidity in the aireverywhere. More water vapor produces stronger precipitation events.
- How does a warmer Earth affect the weather? Extreme weather events are more common and more severe because there is more energy in the system. According to the video, climate "trains the boxer" (i.e., the weather) to throw more punches.
Both the daily weather and seasonal climate can change on multiple timescales. The variation from normal can last from minutes to years; we all can recall an unusually cold day, warm month, or rainy summer. Natural, cyclical variations occur within the climate system, the simplest of these is the seasonal variation that we experience every year. Additionally, even longer-term, large-scale patterns, called oscillations, exist in Earth's climate system. These oscillations take place over periods of time ranging from months to yearseven decades. They can contribute to events of extreme weather such as droughts, floods, and storms. The most familiar of these patterns is probably the El Niño – Southern Oscillation (ENSO). Others include the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Pacific Decadal Oscillation (PDO). All of these patterns oscillate, or swing, between positive and negative states and influence regional and global climate. They contribute to what is known as climate variability or the variations in climate around the average (mean) state of the climate on long-term timescalesbeyond that of individual weather events. To view these patterns of climate variability, go to the Global Climate Dashboard page and click on the climate variability tab.
Move the time slider, located below the graphs, to explore different time frames. Note how the patterns swing above and below the line in a fairly regular pattern.
- What is the timescale of a typical El Niño – Southern Oscillation (ENSO)? It takes one to two years to make the full cycle from warm to cold and back to neutral.
- How frequently does the Arctic Oscillation (AO) change from positive to negative as compared to ENSO? It changes more frequently, on a timescale of weeks to months; however, extended periods occur where it remains in either its positive or negative phase during the winter season.
Global Wild Weather
Over the past decade (2000-2010) we have observed an increase in the frequency, scale (size), duration (length of time), and intensity of extreme weather events around the world. As you probably have seen in the news, these extreme events are devastating to societies in many parts of the globe. The physical impacts of these climate extremes range from local to national. They often impact one or more sectors of society including: agriculture, energy, transportation, water resources, or public health. They cause significant economic loss as well as fatalities.
Why are these events becoming more commonplace? According to the World Meteorological Organization (2011), "While it is impossible to say that an individual weather or climate event was "caused" by climate change, one should anticipate that the magnitudes, frequency and duration of extreme events are likely to be altered as the Earth's atmosphere warms due to the increased concentrations of greenhouse gases." To learn more about how climate change may be fueling increased extreme weather events watch the video: A Home Run on Steroids, Baseball & Climate Change. (Note: the video begins as a blank screen.)
Courtesy of Climate Central and National Center for Atmospheric Research http://www.climatecentral.org/blogs/steroids-baseball-and-climate-change.
Extreme weather events close to home
Once on the map, use the zoom and pan tools to move around the map. Click on the balloons to read more about the events that have taken place in the U.S. When you are done viewing the map, close the page.
What can be done to minimize the risks of damage due to extreme events? In mid-November, 2011, the IPCC (Intergovernmental Panel on Climate Change) issued a special report on managing the risks of extreme events. The report evaluates the role of climate change in altering the characteristics of the extreme weather events. Examples from the IPCC report are listed below.
Examples of extreme events
- Observations since 1950 show changes in some extreme events, particularly daily temperature extremes, and heat waves.
- It is likely (66-100% probability) that the frequency of heavy precipitation will increase in the 21st century over many regions.
- It is virtually certain (99-100% probability) that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout the 21st century on a global scale. It is very likely (90 %-100% probability) that heat waves will increase in length, frequency, and/or intensity over most land areas.
- It is likely that the average maximum wind speed of tropical cyclones (also known as typhoons or hurricanes) will increase throughout the coming century, although possibly not in every ocean basin. However it is also likely—in other words there is a 66-100% probability—that overall there will be either a decrease or essentially no change in the number of tropical cyclones.
- There is evidence, that droughts will intensify over the coming century in southern Europe and the Mediterranean region, central Europe, central North America, Central America and Mexico, northeast Brazil, and southern Africa.
- It is very likely that average sea level rise will contribute to upward trends in extreme sea levels in extreme coastal high water levels.
- Projected precipitation and temperature changes imply changes in flood patterns. However there is low certainty of the exact details at the global scale because of limited evidence and because the causes of regional changes are complex.
Give a wild weather report
Choose one of the wild weather stories from the NOAA climate watch extreme weather events page. Read the article, take notes, and prepare to share the story with your lab team or class in a 2-minute presentation. Summarize the main points in the article and describe the impacts of these weather events on society and life in general. Include a map showing the location of the extreme event.
Finally, read and discuss the full article: Scientific American 2011 Wildest Year on Record. Use the information in the Scientific American article, as well as information gathered from the other resources linked to this page, to answer the Stop and Think questions below.
Stop and Think
- Why do scientists believe extremes of weather are becoming more common?
- What types of weather events are not yet clearly linked to climate change?
- Which extreme weather events are more likely to be influenced by climate variability, such as El Niño or La Niña?
- Provide an article about an extreme weather event of your own interest. Be sure to check the source with your instructor. Several additional sources are listed below. Additional sources of articles on extreme weather events:
- National Center for Atmospheric Research, Currents article Texas–Oklahoma drought: What next for the Southern Plains?
- National Climate Data Center (NCDC) Hazards page Hazards (click the links at the bottom of the page.)
- View an additional summary of extreme weather events, from 2011, which can be accessed here: Green TV - Extreme Weather 2011 (posted December 29, 2011).
- Review the brochure: Why Extremes Matter (Acrobat (PDF) 914kB Jun20 11) (a PDF file. Depending on your browser settings this will open in the same window or it will download to your downloads folder.) Choose one weather phenomenon (e.g., hurricanes, tornadoes, blizzards) to review. Share your findings with your classmates or lab team.
- View a slide show of the Top 10 Hardest Hit states of 2011 and other news at Climate Central.