Thursday, November 21, 2013

Pielke affirms IPCC’s authority but ignores its evidence on extreme weather

Climate Nexus, November 21, 2013 
In a new Guardian post, Roger Pielke, Jr., criticizes recent portrayals of extreme weather in the media, ignoring evidence from the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment Report (AR5). Specifically, he argues that the AR5 offers no evidence that droughts, floods, and wildfires have increased in response to climate change. He also criticizes those who draw a connection between typhoon Haiyan and climate change. In fact, the AR5 provides solid evidence that climate change is affecting all of these extremes or their impacts here and now.
The following is a guest post by Climate Nexus (text in PDF format here):
Pielke affirms IPCC’s authority but ignores its evidence
on extreme weather
In a new Guardian post, Roger Pielke, Jr., criticizes recent portrayals of extreme weather in the media, ignoring evidence from the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment Report (AR5). Specifically, he argues that the AR5 offers no evidence that droughts, floods, and wildfires have increased in response to climate change. He also criticizes those who draw a connection between typhoon Haiyan and climate change. In fact, the AR5 provides solid evidence that climate change is affecting all of these extremes or their impacts here and now.
Pielke, Jr., helpfully acknowledges that the IPCC is a leading authority on climate science. Here’s what it says on extreme weather:
    • The AR5 recognizes clear trends in flood-causing factors like extreme rain and sea level rise, despite the fact that actual trends in flooding are confounded by infrastructure (such as flood-control projects) and land use change.
    • The AR5 describes increases in droughts in specific regions, and suggests a connection to anthropogenic climate change. 
    • The AR5 confirms that North American large wildfires have significantly increased in frequency since the mid 1980s, and the wildfire season has lengthened. These trends are projected to continue. 
    • The AR5 recognizes that sea levels have risen, which contributes to the destructiveness of storms like Haiyan.  It also recognizes increasing temperatures at both the sea surface and the deep ocean. These can contribute to cyclone intensity by making more energy available.
Floods: Climate impacts that worsen floods are on the rise. The IPCC recognizes these trends, even though long-term trends in flooding are extremely difficult to measure. Complex interaction between weather patterns, built infrastructure, and land use change makes it hard to tell the absolute change in flooding over time. But even though the AR5 reports “no widespread observations of changes in flood magnitude and frequency” (WGII, Chapt 3, p. 2), we know that extreme rains contribute to flooding, and that heavy precipitation events have “likely” increased in frequency and/or intensity in Europe and North America (SPM, p. 3). In other continents, there is medium confidence in precipitation changes, and extreme precipitation has increased in more regions than it has decreased.
With respect to the human component, the AR5 states it is “likely” that humans have impacted the water cycle since 1960 (SPM, p. 15), and “more likely than not” contributed to heavy precipitation over most land areas (SPM, p. 5).
Finally, sea level rise of about eight inches this century has been conclusively documented (SPM, p. 9) and attributed to human influence, which contributes to flooding in coastal areas. These factors make it reasonable to conclude that we’re experiencing more flooding than we would in absence of climate change.
Droughts: The AR5 concludes that increased intensity and/or duration of drought has “likely” occurred in many regions since 1970 (SPM p.5), and a further increase in these intense droughts is projected in regions including the American Southwest (WGII Chapter 26, pp. 11, 17). There is low confidence in global-scale changes in drought, but for the affected regions drought represents a major climate impact, one that “more likely than not” is already showing the fingerprints of human influence (SPM, p. 5).
Wildfires: The AR5 states that North America’s large wildfires have occurred “with increasing frequency and duration, within longer wildfire seasons” (WGII, Chapt 26, p. 19). The increase in wildfires is linked to the increase in drought already mentioned, as well as earlier spring snowmelt. Drier soils and longer growing seasons are “likely” to continue to increase and intensify wildfires in Canada and the U.S. (WGII, Chapt 26, p. 6). Wildfires are covered in the second Working Group of the report, which focuses on climate impacts and remains in draft form. The final draft was leaked, and while the quotes may change slightly, the underlying science will not.
Typhoon Haiyan:  Sea level rise worsened the deadly storm surge associated with the typhoon, and this sea level rise is clearly connected to human-caused climate change (SPM, p. 17). The rate of sea level rise is accelerating (SPM, p. 9), making the impacts of typhoons like Haiyan very relevant for discussing our future climate. Warming of the upper ocean also increases the energy available to storms like Haiyan, and the AR5 documents “virtually certain” warming of the ocean from 0-700 m over the past 40 years (SPM, p. 6). While the centennial trends are unclear, the IPCC reported that there has been an upward trend since the 1970s for hurricane power in the western North Pacific where Haiyan struck (WGI Chapt 2, pp. 2-58).
Furthermore, the most recent available draft of the underlying Working Group I chapters states that models predict “substantial increases in the frequency of the most intense cyclones” in the future (WGI Chpt 14 p.14-44). Models predicted more intense cyclones, and we saw (by some measurements) the most intense cyclone ever. Under these circumstances it’s hard to see how Pielke Jr. can fault the New York Times for stating that Haiyan is “consistent with” climate predictions.
If the IPCC’s AR5 report is the authority on climate science, which Pielke, Jr., affirms that it is, there is ample evidence to support the connections that many public figures are increasingly making between climate change and extreme weather events.
Also be sure to see the post by Dana Nucitelli in the Guardian: "Will extreme weather like super typhoon Haiyan become the new norm?"
And this by Michael Mann at Huffington Post: "Super Typhoon Haiyan: Realities of a Warmed World"
Some earlier posts by Climate Nexus:
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