Intergovernmental Panel on Climate ChangeBy Bill Dawson
Texas Climate News

It’s now “unequivocal” that the climate system is warming and “many observed changes are unprecedented over decades to millennia,” the world’s leading body of climate scientists recently declared in the initial installment of its first major summary of research findings since 2007.

“Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes,” the U.N.-sponsored Intergovernmental Panel on Climate Change stated. The group added that it is now “extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”

In the IPCC’s numerical ranking of confidence levels, “extremely likely” means at least 95 percent. As the Washington Post noted, 95 percent is “as sure as [scientists] are that cigarette smoking causes cancer.”

In another conclusion included in a selected list of “headline statements” from its lengthy report, the IPCC added: “Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.”

Looking ahead, the IPCC assigned these confidence levels to key projections for the latter part of the century:

“Virtually certain” (99 to 100 percent probability):

  • “Warmer and/or fewer cold days and nights over most land areas.”
  • “Warmer and/or more frequent hot days and nights over most land areas.”

“Very likely” (90 to 100 percent):

  • “Warm spells/heat waves – frequency and/or duration increases over most land areas.”
  • “Heavy precipitation events – increase in the frequency, intensity, and/or amount of heavy precipitation.” (Over “most land areas.”)
  • “Increased incidence and/or magnitude of extreme high sea level.”
IPCC WG1 report, 2013

The IPCC found that each of the past three decades has been among the warmest since instrumental temperature records began and likely the warmest in the Northern Hemisphere in more than 1,000 years. Climate Central, a non-profit organization staffed by journalists and scientists, prepared this graphic.

The IPCC’s “headline statements” are here, its “Summary for Policymakers” is here and the entire report is here. This report, on the science of climate change, is the first of three such summaries that will be issued in coming months. The second will cover the impacts of climate change and the third will address options for limiting human-caused changes to climate system “through limiting or preventing greenhouse gas emissions and enhancing activities that remove them from the atmosphere.”

What does the first report, on the science of climate change itself, mean for Texas? Texas Climate News asked six scientists and one policy expert on climate issues to offer their thoughts.

John Nielsen-Gammon
Regents professor of atmospheric sciences and Texas state climatologist, Texas A&M University

Are Texas droughts going to get better, get worse or stay about the same? The latest IPCC report presents a mixed message. On one hand, it notes that there has been a decreasing drought frequency in the central United States over the past half-century. Yet the projections for streamflow and soil moisture, the quantities that really matter during a drought, situate Texas as one of the most vulnerable places in the world for increasing dryness.

The IPCC’s assessment of reduced observed drought was based on a paper that analyzed data through 2008. In Texas, the numbers are similar: the observed trend through 2008 is for 1.5 fewer months per decade in drought, and the trend for the August Palmer Drought Severity Index (PDSI) over the same period has an improvement in the index of 0.8 per century. For reference, zero is normal and minus 4 is extreme drought.

But four of the past five years have been drought years in Texas. When I update the numbers, I find that the PDSI trend of plus 0.8 per century has flipped to minus 0.1 per century, and the duration of drought is declining by only 0.3 months per decade. In fact, if the Texas drought lasts through December, the decline will be just 0.1 months per decade. This drought has almost singlehandedly put an end to the trend of reduced drought frequency and intensity that Texas had been experiencing.

The latest IPCC report is mostly just an incremental update of something we already knew. The [continuing] drought of 2011–20xx has taught us something we didn’t know: Rather than being a thing of the past, Texas drought can be worse than we imagined.

Jurgen Schmandt
Professor emeritus, Lyndon B. Johnson School of Public Affairs, University of Texas; co-editor, The Impact of Global Warming on Texas, 2nd edition (University of Texas Press, 2011)

For Texas I see two important facts emerging from the 2013 report. One, sea-level rise will progress faster than we previously thought. This is due to the melting of the ice shield in Antarctica and Greenland. Two, assessing probable impacts of climate change has been scaled down to, as Gerald North [professor of atmospheric sciences and oceanography at Texas A&M University and co-editor of The Impact of Global Warming on Texas] put it, Texas-county-sized chunks of land.

Thus we have much better tools to project, for example, water supply in the Lower Rio Grande basin. It will take time and effort to apply the new tools to precise locations. But the 2012 statement in the State Water Plan – we cannot do more than wait for better forecasts – is no longer defensible. We can make reliable forecasts of water supply and demand to the year 2060, and take action now for doing more with less, at the farm, at the basin-level, and in the city.

John Anderson
Professor of oceanography and academic director of the Shell Center for Sustainability, Rice University

Even before the 2013 IPCC report was released, the scientific community had reached strong consensus that the rate of global sea-level rise was accelerating at an alarming rate, from a long-term average of 0.5 millimeters per year for the past 4,000 years to the current rate of just over 2.5 millimeters per year in the northern Gulf of Mexico. The explanation for this increase is also established – heating and expansion of the oceans and melting of glaciers and ice sheets.

For those skeptics who argue that the earth’s climate has always changed, it is the rate of change that is disturbing. Yes, sea level was rising just as fast and faster before 8,000 years ago, but it is now clear that humans are the cause of the current change. With the rapid acceleration of sea-level rise comes unprecedented change in our coast.

Research has shown that barrier islands of the upper Texas coast are eroding at nearly twice the rate of the past 1,000 years and, based on the latest IPCC estimates for sea-level rise this century, this is only the beginning of dramatic change. Our children and grandchildren will without doubt inherit a radically changing coast.

Larry McKinney
Executive director, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi

While we (HRI) may recognize and understand, better than most, the broader issues and science behind the new IPPC report, we are not expending any energy debating it. Our focus is on the practical implications to the economic and environmental health of the state if we ignore one of the most obvious symptoms of climate change, sea-level rise.

Regardless of where you are in that debate, the fact is that sea level, as measured at Pier 21 in Galveston, has risen two feet since 1908. Half of that was due to subsidence but the other half was due to climate change. Anyone who wants to stick their head in the sand about that reality is likely to drown if they keep it there too long.

Katharine Hayhoe
Director, Climate Science Center, and associate professor of public administration, Texas Tech University

The new [IPCC] report confirms the broad conclusions reached by previous reports – that climate is changing, humans are responsible and impacts are already visible today.

The report adds an additional layer of certainty: It is now “extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.” Scientists can’t really be any more certain than that!

The report also goes a step further than previous reports by directly linking carbon emissions to global temperature thresholds and impacts. The report is explicit: if we emit X amount of cumulative carbon emissions, we will see Y amount of temperature change, and impacts will increase with that temperature change. This clearly connects human choices made today to impacts that will occur in the future.

What does this mean for Texas? The IPCC reports do not zoom in to the regional or local scales; do not look to the report for updated projections of climate change or impacts specific to Texas itself. That is the role of the U.S. National Climate Assessment, the third version of which is in its final review and will be released shortly. However, the National Assessment is based on the fundamental science and modeling work presented in the IPCC report. It provides the basis we can then work from to assess the impacts of climate change on Texas and the U.S. as a whole.

Ron Sass
Fellow in global climate change, James A. Baker III Institute for Public Policy, and Harry C. and Olga K. Wiess professor of natural sciences emeritus, Rice University

The recently published Fifth Assessment Report of the IPCC summarizes and consolidates work on various aspects of climate change found in 9,200 worldwide-published scientific studies. Major conclusions in the report, somewhat understated, include the statements that “warming of the climate system is unequivocal” and that “it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century”.

In the very precise phrasing of the IPCC, “extremely likely” corresponds to a 95 percent probability the statement is correct. In the conservative world of science, that degree of probability reflects the point where a person can bet the farm without fear of losing it.

Yet three days after the report was released, Bryan Shaw, chairman of the Texas Commission on Environmental Quality, stated at The Texas Tribune Festival in Austin, “What we see is greater and greater uncertainty” in the climate models. He also pointed out the often-used misinterpretation of the data that global warming has not occurred since 1998. He also averred that carbon dioxide couldn’t be the cause of warming because water vapor is the major greenhouse gas. It is, but that does not relieve carbon dioxide and other radiatively active gases from tipping the scale.

Shaw is not alone in his views. Others, some in positions of great political power, reacted similarly. Editorials and reports found in the Washington Times, the Washington Examiner, the Tucson Citizen and the Daily Mail [of Britain], to name a few of several news sources, all claimed the world is not warming but is actually cooling and will continue to get colder for another 40 years.

I worry about this lack of trust that is expressed by some over the contents of a report representing the consensus scientific findings of thousands of climate experts. I worry about the misinformation that is expressed by some over climate change. I worry about the fact that this misinformation and lack of trust in science is causing our state and national leaders to do nothing to counteract the self-inflicted environmental pain that is demonstrably heading our way. But what I worry most about is that those who will suffer most from the results of our inability to comprehend what our actions are doing, my children and grandchildren, will live in a world that is so much less desirable than the one I have had the privilege to live in.

Andrew Dessler
Professor of atmospheric sciences, Texas A&M University; 2011 Google science communication fellow on the science of climate change

This week, a new report from the Intergovernmental Panel on Climate Change confirms what we already know: The Earth is warming, humans are mainly responsible, and future warming could be serious. This is exactly the same thing the previous four IPCC reports said. In fact, one could argue that climate science has not significantly changed since it was first hypothesized that combustion of fossil fuels could change the climate – in 1896.

And it’s not just my opinion: Of the dozens of atmospheric scientists in our state, approximately zero of them are skeptical of this mainstream view of climate science. Our department and the Climate Systems Science group at the University of Texas even have statements on their websites confirming our agreement.

So why is there such a disconnect between what scientists think and the public debate? What actually motivates most “climate skeptics” is a fear of climate policy. If climate change is true and we decide to reduce emissions, then it will almost certainly require intervention by the government into the energy market. For some, that idea is so repugnant that the only conclusion is that the problem must not exist.

Given this, it’s important to remember history. In the early 1970s, Congress passed the Clean Air Act, which drastically improved air quality, the benefits of which are more than 30 times the cost. And the Montreal Protocol, which phased out ozone-depleting chemicals, was a profoundly cost-effective policy that saved the ozone layer.

I am confident that the same thing will happen here. If we put our minds to it, we can solve the climate problem and prosper, too. Only someone profoundly pessimistic would bet against American ingenuity.


Disclosure: Bill Dawson, editor of Texas Climate News, wrote the Introduction chapter for The Impact of Global Warming on Texas, 2nd edition. The Houston Advanced Research Center, which publishes TCN, commissioned the book. TCN is written and edited by journalists who are not HARC employees and make all editorial decisions without direction or influence from HARC, its funders or partners.

Image credits: IPCC (logo), Climate Central (chart)