Large urban agglomerations inevitably lead to air pollution. But despite the significant impacts on human health and climate, we lack systematic measurements of air pollution in many cities. Megan L Melamed, Tong Zhu and Liisa Jalkanen discuss a new global assessment that illuminates the knowns and unknowns.
Rising sea levels will eventually threaten many coastal cities. But a dominant focus on the long-term endgame should not unduly restrict our options to deal with the more immediate consequences of climate change, says Richard Little .
Earth behaves as a complex system. Complex systems can respond abruptly to changes within the system - these abrupts changes can be highly non-linear. There is strong evidence that the Earth system is prone to such abrupt changes.
Human-induced global change has pushed the Earth system into a no-analogue state — where climatic and other environmental conditions are outside of the range of the last half million years (at least), increasing the likelihood of unpredictable changes with potentially harmful consequences. Exploring and quantifying Earth system interactions is therefore extremely important. The Earth system perspective demands a new scientific approach and innovative conceptual and technical tools. Separate Earth system components, properties and processes — such as the composition and circulation pattern of the atmosphere — still need to be investigated, but should be studied as integral parts of a system, so as to understand their interactions and feedbacks. Furthermore, in the era of global change, humanity must also be considered a part of the Earth system. Indeed, IGBP includes the human social, cultural and economic systems as within the Earth system.
This issue’s cover story puts 2000 years of regional temperature histories into perspective. Also featured: two full-spread maps visualising the PAGES 2k regional temperature records and ocean acidifi...