Pinyon pine forests that usually absorb CO2 from the atmosphere to grow near Los Alamos, N.M., in the region Christopher Schwalm and his colleagues studied, had already begun to turn brown from drought stress in the image at left, in 2002, and another photo taken in 2004 from the same vantage point, at right, show them largely grey and dead. Credit: Craig Allen, U.S. Geological Survey
Though the last time western North America saw a drought as severe as the one it experienced in 2000-2004 was 800 years ago, such conditions could become normal by the end of the century. This drying will shift western North America’s natural carbon cycle into reverse, from absorbing CO2 overall today to emitting it and worsening climate change further. That’s according to a paper by Christopher Schwalm, from Northern Arizona University in Flagstaff, and his colleagues published in the research journal Nature Geoscience on Sunday. “What we now call a drought event will become an abnormally wet episode by the end of the 21st Century,” Christopher told Simple Climate.
With drought in the US Midwest currently drawing much attention, the 2000-2004 drought might have slipped from some memories – even though they led to a natural disaster being declared in some areas. Our views of these events are bound to change as droughts become more regular as the world heats up, even though warmer air can contain more water vapour. “The changing climate means that the atmosphere can carry more water,” Christopher said. “However, precipitation will happen in spurts, more intensive rainfall in a relatively short period of time. Similarly, the amount of time between such events is expected to increase. So we will see fewer but more intense rainfall events, and therefore more droughts.”
The “turn of the century” drought has been remembered and closely studied by researchers looking at what it tells us about our climate. However, that research hasn’t been brought together to understand what it means for how much carbon plants are taking up, Christopher said. So he set out with a team of nine other US and Canada-based researchers to fill that gap. But to do so meant working with several sets of measurements that covered different areas and time periods. “Despite having various satellite data sources, global monitoring networks, and the like, our biggest challenge was how to piece together what data we do have and still paint a comprehensive picture,” Christopher explained. Read the rest of this entry »
