Global warming: What we know

A potential for abrupt, unpredictable, and potentially irreversible changes with highly damaging impacts

February 2014 marked the 29th consecutive year with global temperatures running above the 20th century average. Map courtesy NASA.

Staff Report

FRISCO — Making informed choices about climate change and greenhouse gas emissions will help reduce risks for present and future generations and help communities adapt to climate change, scientists said last week, announcing a new initiative to inform the public about climate change.

Published by the American Association for the Advancement of Science, the paper explains that humanity has successfully responded to other major environmental challenges such as acid rain and the ozone hole with benefits greater than costs. ”

Today, scientists working with economists believe there are “ways to manage the risks of climate change while balancing current and future economic prosperity, the authors wrote.

Saying that the current rate of warming is beyond the range of what has been experienced over the past millions of years, the scientists warned that inaction risks pushing the Earth’s climate system toward abrupt, unpredictable, and potentially irreversible changes with highly damaging impacts.

“The range of uncertainty for the warming along the current emissions path is wide enough to encompass massively disruptive consequences to societies and ecosystems …  there is a real risk, however small, that one or more critical parts of the Earth’s climate system will experience abrupt,  unpredictable and potentially irreversible changes. Disturbingly, scientists do not know how much warming is required to trigger such changes to the climate system,” the scientists said.

Some excerpts from the paper:

  • Extreme weather is not just an abstract concept. It is a reality that affects people across the country. In 2013, two out of three Americans said weather in the U.S. has been worse over the past several years, up 12 percentage points since spring 2012. Many (51%) say weather in their local area has been worse over the past several years. Not surprisingly, then, the gap between what we know as scientists (that global warming impacts are here and now) and what Americans perceive is narrowing: About six in 10 Americans say, “Global warming affecting weather in the U.S.”
  • The oceans are absorbing much of the CO2 that smokestacks and tailpipes emit into the atmosphere. As a result, the oceans are rapidly acidifying, with early impacts on shelled organisms such as oysters already documented. The current acidification rate is likely the fastest in 300 million years.
  • Extinctions are likely to increase, as climate change combines with other human-related environmental pressures. Moreover, the impacts of climate change on ecosystem processes such as decomposition, plant production and nutrient cycling ␣ processes that determine how much fossil fuel-derived CO2 the land and ocean will continue to sequester in coming decades ␣ remain largely unknown.
  • Sea level rise has also accelerated, making storm surges higher and pushing salt water into the aquifers that coastal communities depend on for fresh water, and increasing the extent of coastal flooding. Over the last two decades, sea levels have risen almost twice as fast as the average during the 20th century.xx Salt-water intrusion can be witnessed in southern Florida, where sea level rise is contributing to salt water infiltration of coastal wells.
  • Since 1950, heat waves worldwide have become longer and more frequent.xxv One study indicates that the global area hit by extremely hot summertime temperatures has increased 50-fold,xxvi and the fingerprint of global warming has been firmly identified in these trends.xxvii In the U.S., new record high temperatures now regularly outnumber new record lows by a ratio of 2:1.
  • In Antarctica, marine ice/ice sheet instability threatens abrupt and large losses from both the West Antarctic Ice Sheet (WAIS) and portions of the East Antarctic Ice Sheet. Any significant ice loss likely would be irreversible for thousands of years. Simulations of warming and ice loss during earlier warm periods of the last 5 million years indicate these areas can contribute 23 feet of sea level rise.



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