As the city of New Orleans struggles to rebuild from the devastation of Hurricane Katrina (right), researchers are learning more about weather, climate and their impact on society.
Scientists from the National Center for Atmospheric Research (NCAR) and other institutions are converging in New Orleans this week to present their latest findings at the annual meeting of the American Meteorological Society. Here are some of the program highlights.
Hurricanes and Climate. The last two years have seen a burst of research on the relationship between hurricanes and climate, especially for North Atlantic storms. While much work has focused on how human-induced climate change affects hurricanes, less is known about how hurricanes affect climate. Scientists are working to better quantify the roles of natural and human-related factors in shaping hurricanes.
Climate Shift. Earth’s climate underwent a major shift in the mid-1970s, as global temperatures began a warming trend that continues today. The largest changes were centered in and near the Pacific Ocean. Scientists have debated for years whether this shift is caused by increasing greenhouse gases, natural climate variability or some mix of the two. According to a new set of climate simulations, increased emissions from fossil-fuel burning set the stage for the climate shift in the 1960s, but natural variations delayed it until the 1970s.
Monsoon Changes. One aspect of global climate shift in the 1970s was a change in the Asian summer monsoon, which brings life-giving moisture to one-third of the world’s population. The shift pushed the jet stream’s typical summer position over East Asia southward, which has led to more flooding in southern China and more drought in northern China. New computer modeling links the post-1970s rearrangement in Chinese rainfall patterns to the global increase in greenhouse gases and aerosols, as well as to warm tropical oceans.
Worldwide Runoff. Some studies have pointed to an increase in the total worldwide runoff of water from land to ocean over the last century, yet there are many gaps in the global record. New NCAR research, which contradicts prior work, shows the total discharge of water from land to the world’s oceans has actually decreased since 1949. Among the world’s major ocean basins, only the Arctic shows an increase, possibly due to the melting of snow cover and soil-bound ice or a decrease in evaporation. In the other basins, the NCAR analysis suggests that runoff is decreasing mainly because of more widespread drought and other changes in precipitation.
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Image courtesy of NASA