Blog on Science Cafe, September 16, 2014 at Magpie Pizza

Rodrigo Valdés

Over last decades global change has been one of the most important fields of study for researchers of different disciplines. This is because its development and impacts include different natural and anthropogenic processes that are very difficult to analyze e.g. potential effect on people, potential to slow or stop it, influence on so many aspects of society, etc. Despite now there is a better understanding about the possible functioning of global climate change, still there are a lot of questions that must be answered in order to generate appropriate adaptation and mitigation activities. For instance, how will global warming impact future climate scenarios?. Or what does climate change mean for the future of our planet?. The Regents Professor Jonathan Overpeck from Geosciences and Atmospheric Sciences departments at the University of Arizona has been working on understanding the impacts of global warming in climate extremes over the southwestern United States (SWUS), but also in a global scale. He has published more than 170 papers in climate and the environmental sciences and served as a coordinating lead author for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (2007). On Sept 16^th 2014, Professor Overpeck presented a talk titled “Global Warming: Implications for Changing Climate Extremes”, where it was possible to observe recent results about the impact of global warming on climate extremes. The talk was divided among four different types of impacts: 1) Temperatures, 2) Precipitation, 3) Droughts, and 4) Hurricanes (Cyclones).

Climate Event 1: “More frequent and longer warm spells and heat waves”. This pattern has been observed in many regions of the world, i.e. Australia, Europe, and SWUS. Global maps of increased number of warm days/nights and decreased number of cold days/nights showed that almost all the world is getting warmer. These increased changes in temperature patterns have likely been forced by human activity and it is highly probable that in the future will be a sure impact for the SWUS.

Climate Event 2: “More frequency, intensity, and amount of heavy precipitation”. Because increased rates of evaporation, the atmosphere has now more moisture that affects precipitation patterns, which is also influencing the intensity and magnitude of floods. For example, heavy storms pounded Arizona on Sept 8^th 2014, where daily rainfall of 1.26 in. was recorded at the Tucson Airport. The National Weather Service stated that this recent event broke the old record of 0.94 in. observed in 1919.

Climate Event 3: “Increase in intensity and duration of droughts”. Droughts are a combination of precipitation and temperature interactions. NOAA indicated that between 2010 and present droughts have generated economic impacts of more than US $40 billion and the loss of 218 human lives in the United States alone. Additionally the longest drought in SWUS since raingauges records exist continues (15-year drought), and the impacts of this phenomenon can be clearly observed in Lake Powell. Mega-droughts have more intensity and duration, and they are powerful, dangerous and hard to detect. They have occurred in the past, and they are still out there, i.e. the chances of having a three-decade-long drought is about 20%-50-% for SWUS in the coming century.

Climate Event 4: “Increase in intense tropical cyclone (hurricane) activity”. This phenomenon occurs mainly in the in the Atlantic Ocean, and their statistical changes are very hard to detect in the data from elsewhere because observations are still too short. This also has a certain degree of relation to precipitation intensity, because storms should lead to more intense rain.

According to Overpeck’s conclusions most of the changes stated above are currently happening around the entire globe; however, each one of these changes has regional components. Some of them have been influenced by human activity, and it is likely that in the future they will be almost a sure bet, which means that anthropogenic warming will probably make all of these changes worse. However, there is still uncertainty about what is the bottom line for these changes, how strong they will be impacting our planet, what the human action can make to minimize climate change?, and where will this lead next? .