AbruptChangesInClimateInTheTwentiethCentury

Complex interactions in the climate system can give rise to strong positive feedback mechanisms that may lead to sudden changes in climate. These abrupt climate changes are almost impossible to predict. As a result, human and environmental systems are often caught unaware and without the necessary mechanisms for adaptation. The well-studied abrupt and prolonged drought in the Sahel, for example, has vastly affected the region and its people. Apart from the Sahel, however, studies on abrupt climatic changes in other regions of the world especially in the 20th century are limited. Here we analyze historical temperature and rainfall observation data using wavelet analysis to detect regions that may have undergone sudden changes in climate. We isolate regions wherein anomalous climate changes deviate persistently from the 1901-2000 time series average. Our results show that in the 20th century, many regions in the world aside from the Sahel may have experienced sudden changes in rainfall. Our results also indicate numerous large, abrupt changes in temperature that are globally widespread in the last two decades of the 20th century. Identifying these regions of large, sudden climate changes is a good first step in analyzing the underlying dynamics of a system's loss of resilience and may complement current and future modeling studies. Further, knowing that these regions are particularly vulnerable to abrupt climate change may help in the development of strategies not only for adaptation but also for resilience management in these environmental systems. Lastly, these maps give us a hint of the magnitude of global abrupt changes in climate in the 20th century. They give us a picture of what has happened and what can happen. With the projected changes in climate in the next 100 years, the possibility of increasing loss of resilience in these regions as well as other regions that were not previously vulnerable is almost undeniable. These maps reiterate the need for understanding the dynamics of environmental systems and addressing the problem of its continuing loss of resilience.