“The first decade of the 21st century was the warmest decade recorded since modern measurements began around 1850. It saw above-average precipitation, including one year – 2010 – that broke all previous records. It was also marked by dramatic climate and weather extremes such as the European heatwave of 2003, the 2010 floods in Pakistan, hurricane Katrina in the United States of America (USA), cyclone Nargis in Myanmar and long-term droughts in the Amazon Basin, Australia and East Africa. Many of these events and trends can be explained by the natural variability of the climate system. Rising atmospheric concentrations of greenhouse gases, however, are also affecting the climate. Detecting the respective roles being played by climate variability and human- induced climate change is one of the key challenges facing researchers today.”