Have We Passed the Climate Change Tipping Point?

By Earl J. Ritchie, Lecturer, Department of Construction Management

A few years ago, 400 parts per million for carbon dioxide was widely cited as the tipping point for climate change. Now that we have passed that value, it has become common to say that it wasn’t really a tipping point, that it was symbolic or a milestone.

Whether it’s a tipping point or a milestone, we have decisively passed it and CO2 levels appear certain to continue higher. Ralph Keeling, the originator of the famous Keeling Curve, said “it already seems safe to conclude that we won’t be seeing a monthly value below 400 ppm this year – or ever again for the indefinite future.”

Let’s consider what a tipping point actually is. The IPCC describes it as “abrupt and irreversible change.” Lenton, et al. say it “will inevitably lead to a large change of the system, i.e., independently of what might happen to the controls thereafter.” In other words, past the tipping point there will be drastic changes even if we stop emitting CO2. Rather than staying “well below 2 degrees Celsius above pre-industrial levels” as is the target of the United Nations Framework Convention on Climate Change (UNFCCC), there could be warming of several degrees, with associated sea level rise and rainfall changes.

tipping-point

Source: Alchemy 4 the Soul

In contrast to these definitions, others say climate change at projected CO2 levels may be reversible. Reversibility is important because otherwise it’s impossible, or at least very difficult, to do anything once you have passed the tipping point. I’ll return to this.

Where do we stand on CO2?

Atmospheric CO2 has not only been increasing; it has been accelerating. The 2001-2016 annual average increase is double that of 1960-1980. As pointed out in an earlier post, commitments under the UNFCC Paris Agreement do not decrease global CO2 emissions, so it is virtually certain that CO2 concentrations will continue to rise.

Much has been made of the potential impact of Trump’s policies on CO2 emissions. The frequently quoted Lux Research analysis of Clinton and Trump policies projected a difference well under a billion metric tons in 2025. This is just over 1% of the world total under the Paris Agreement commitments. The difference is not significant insofar as it relates to tipping mechanisms.

Climate tipping mechanisms

There are multiple possible tipping mechanisms, some of which are shown on the map below. Several of these are occurring today: Arctic sea ice loss, melt of the Greenland ice sheet and boreal forest dieback (and range shifts) are well documented. The extent of permafrost loss, instability of the West Antarctic Ice Sheet and slowing of the Atlantic deep water formation (also called Atlantic Thermohaline Circulation or Atlantic Meridional Overturning Circulation) are less well supported, but there are indications that these are occurring.

These mechanisms are not directly dependent on CO2 concentration; they are triggered by warming alone. Given the amount of warming in recent decades, it is not surprising that they are occurring.

3-1200x739 (1)

Source: Lenton, et al. PNAS 2008

The effects of potential tipping mechanisms are difficult to judge. It’s generally agreed that Arctic sea ice melting is a positive feedback event. Less ice means a darker ocean and more warming. Others are not so clear-cut.

For example, boreal forests, which represent about one-third of the world’s forest cover, are carbon sinks but have variable reflectance depending upon the season, snow cover and vegetation type. Compared to tundra and deciduous forests, they have a net warming effect. The extent to which they will migrate due to warming, and the type of vegetation which will succeed them, are speculative.

Further uncertainty exists because climate effects interact. It is possible to have a cascade, in which increased warming from exceeding one tipping point triggers another.

Is climate change reversible?

The IPCC considers some additional warming irreversible. They say “Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases.”

Per the models cited in the IPCC assessments, anthropogenic climate change can be halted at 2 degrees, although this scenario requires negative industry and energy-related CO2 emissions later this century. By this interpretation, a tipping point has not been reached.

Accomplishing the 2 degree scenario may be difficult. The world’s track record in emissions reductions is poor. According to Friedlingstein, et al., “Current emission growth rates are twice as large as in the 1990s despite 20 years of international climate negotiations under the United Nations Framework Convention on Climate Change (UNFCCC).”

There has been a reported flattening in fossil fuel emissions for the past couple of years, due primarily to reported coal reductions in China. It remains to be seen whether this is the beginning of a reversal. Even so, emissions would have to decrease rapidly to meet even the 2 degree goal.

Prescriptions for reversal of global warming include proposed geoengineering methods for removing CO2 from the atmosphere and cooling the Earth by reflecting or blocking solar radiation. These do not mean that a tipping point was not passed. In the analogy shown in the cartoon above, one can push the rock back up the hill even after it has rolled to the bottom.

Have we passed the tipping point?

Observed advances in multiple tipping mechanisms certainly raise the question whether the tipping point has been passed. However, these mechanisms are accounted for to at least some degree in climate models, so interpreting that we have passed the tipping point requires that the models understate warming effects.

This is essentially an issue of the sensitivity of climate, that is, how much warming results from a given greenhouse gas concentration. The IPCC’s analysis concludes the likely range of equilibrium sensitivity for doubling of CO2 is 1.5 degrees to 4.5 degrees. As the graph below shows, there is reasonable probability that it could be substantially higher.

simulated-climate-sensitivity

Source: NASA Earth Observatory

If the actual value of sensitivity falls in these higher ranges, warming will be greater than predicted by the IPCC models and a tipping point or points may have been exceeded. I’m not sure that anyone actually knows the answer, which leaves me with the unsatisfactory conclusion of not having answered the question I have raised.

Regardless of whether we have passed the tipping point, continued warming, rainfall pattern changes, significant sea level rise and continued northward and vertical migration of plant and animal species in the Northern Hemisphere seem certain. We are looking at a changed world and must adapt to it.

Not an excuse for inaction

One should not view the possibility that we have passed a significant tipping point as a reason for inaction. Although I remain somewhat skeptical of the degree of human contribution to climate change, it is prudent to take reasonable actions that may reduce the problem. In addition, there are multiple possible tipping points with different thresholds. Exceeding one does not mean you cannot avoid another.


Earl J. Ritchie   is a retired energy executive and teaches a course on the oil and gas industry at the University of Houston. He has 35 years’ experience in the industry. He started as a geophysicist with Mobil Oil and subsequently worked in a variety of management and technical positions with several independent exploration and production companies. Ritchie retired as Vice President and General Manager of the offshore division of EOG Resources in 2007. Prior to his experience in the oil industry, he served at the US Air Force Special Weapons Center, providing geologic and geophysical support to nuclear research activities.

Fact Checking The 97% Consensus On Anthropogenic Climate Change

By Earl Ritchie, Lecturer, Department of Construction Management

The claim that there is a 97% consensus among scientists that humans are the cause of global warming is widely made in climate change literature and by political figures. It has been heavily publicized, often in the form of pie charts, as illustrated by this figure from the Consensus Project.

ritchie-1_121416

The 97% figure has been disputed and vigorously defended, with emotional arguments and counterarguments published in a number of papers. Although the degree of consensus is only one of several arguments for anthropogenic climate change – the statements of professional societies and evidence presented in reports from the Intergovernmental Panel on Climate Change are others – there is data to suggest that support is lower. In this post, I attempt to determine whether the 97% consensus is fact or fiction.

The 97% number was popularized by two articles, the first by Naomi Oreskes, now Professor of Science History and Affiliated Professor of Earth and Planetary Sciences at Harvard University, and the second by a group of authors led by John Cook, the Climate Communication Fellow for the Global Change Institute at The University of Queensland. Both papers were based on analyses of earlier publications. Other analyses and surveys arrive at different, often lower, numbers depending in part on how support for the concept was defined and on the population surveyed.

This public discussion was started by Oreskes’ brief 2004 article, which included an analysis of 928 papers containing the keywords “global climate change.” The article says “none of the papers disagreed with the consensus position” of anthropogenic global warming. Although this article makes no claim to a specific number, it is routinely described as indicating 100% agreement and used as support for the 97% figure.

In a 2007 book chapter, Oreskes infers that the lack of expressed dissent “demonstrates that any remaining professional dissent is now exceedingly minor.” The chapter revealed that there were about 235 papers in the 2004 article, or 25%, that endorsed the position. An additional 50% were interpreted to have implicitly endorsed, primarily on the basis that they discussed evaluation of impacts. Authors addressing impacts might believe that the Earth is warming without believing it is anthropogenic. In the article, Oreskes said some authors she counted “might believe that current climate change is natural.” It is impossible to tell from this analysis how many actually believed it. On that basis, I find that this study does not support the 97% number.

The most influential and most debated article was the 2013 paper by Cook, et al., which popularized the 97% figure. The authors used methodology similar to Oreskes but based their analysis on abstracts rather than full content. I do not intend to reopen the debate over this paper. Instead, let’s consider it along with some of the numerous other surveys available.

Reviews of published surveys were published in 2016 by Cook and his collaborators and by Richard S. J. Tol, Professor of Economics at the University of Sussex. The 2016 Cook paper, which reviews 14 published analyses and includes among its authors Oreskes and several authors of the papers shown in the chart below, concludes that the scientific consensus “is robust, with a range of 90%–100% depending on the exact question, timing and sampling methodology.” The chart shows the post-2000 opinions summarized in Table 1 of the paper. Dates given are those of the survey, not the publication date. I’ve added a 2016 survey of meteorologists from George Mason University and omitted the Oreskes article.

The classification of publishing and non-publishing is that used by Cook and his collaborators. These categories are intended to be measures of how active the scientists in the sample analyzed have been in writing peer-reviewed articles on climate change. Because of different methodology, that information is not available in all of the surveys. The categorization should be considered an approximation. The chart shows that over half the surveys in the publishing category and all the surveys in the non-publishing category are below 97%.

ritchie-2_121416

Cook is careful to describe his 2013 study results as being based on “climate experts.” Political figures and the popular press are not so careful. President Obama and Secretary of State John Kerry have repeatedly characterized it as 97% of scientists. Kerry has gone so far as to say that “97 percent of peer-reviewed climate studies confirm that climate change is happening and that human activity is largely responsible.” This is patently wrong, since the Cook study and others showed that the majority of papers take no position. One does not expect nuance in political speeches, and the authors of scientific papers cannot be held responsible for the statements of politicians and the media.

Given these results, it is clear that support among scientists for human-caused climate change is below 97%. Most studies including specialties other than climatologists find support in the range of 80% to 90%. The 97% consensus of scientists, when used without limitation to climate scientists, is false.

In the strict sense, the 97% consensus is false, even when limited to climate scientists. The 2016 Cook review found the consensus to be “shared by 90%–100% of publishing climate scientists.” One survey found it to be 84%. Continuing to claim 97% support is deceptive. I find the 97% consensus of climate scientists to be overstated.

An important consideration in this discussion is that we are attempting to define a single number to represent a range of opinions which have many nuances. To begin with, as Oreskes says, “often it is challenging to determine exactly what the authors of the paper[s] do think about global climate change.” In addition, published surveys vary in methodology. They do not ask the same questions in the same format, are collected by different sampling methods, and are rated by different individuals who may have biases. These issues are much discussed in the literature on climate change, including in the articles discussed here.

The range of opinions and the many factors affecting belief in anthropogenic climate change cannot be covered here. The variety of opinion can be illustrated by one graph from the 2013 repeat of the Bray and von Storch survey showing the degree of belief that recent or future climate change is due to or will be caused by human activity. A value of 1 indicates not convinced and a value of 7 is very much convinced. The top three values add to 81%, roughly in the range of several other surveys.

ritchie-3_121416

Even though belief is clearly below 97%, support over 80% is strong consensus. Would a lower level of consensus convince anyone concerned about anthropogenic global warming to abandon their views and advocate unrestricted burning of fossil fuels? I think not. Even the 2016 Cook paper says “From a broader perspective, it doesn’t matter if the consensus number is 90% or 100%.”

Despite the difficulty in defining a precise number and the opinion that the exact number is not important, 97% continues to be widely publicized and defended. One might ask why 97% is important. Perhaps it’s because 97% has marketing value. It sounds precise and says that only 3% disagree. By implication, that small number who disagree must be out of the mainstream: cranks, chronic naysayers, or shills of the fossil fuel industry. They are frequently described as a “tiny minority.” It’s not as easy to discount dissenters if the number is 10 or 15 percent.

The conclusions of the IPCC are the other most often cited support for anthropogenic climate change. These conclusions are consensus results of a committee with thousands of contributors. Although this is often viewed as a monolithic conclusion, the nature of committee processes makes it virtually certain that there are varying degrees of agreement, similar to what was shown in the Bray and von Storch survey. The Union of Concerned Scientists says of the IPCC process “it would be clearly unrealistic to aim for unanimous agreement on every aspect of the report.” Perhaps this is a subject for another day.

Earl J. Ritchie is a retired energy executive and teaches a course on the oil and gas industry at the University of Houston. He has 35 years’ experience in the industry. He started as a geophysicist with Mobil Oil and subsequently worked in a variety of management and technical positions with several independent exploration and production companies. Ritchie retired as Vice President and General Manager of the offshore division of EOG Resources in 2007. Prior to his experience in the oil industry, he served at the US Air Force Special Weapons Center, providing geologic and geophysical support to nuclear research activities.

UH Energy is the University of Houston’s hub for energy education, research and technology incubation, working to shape the energy future and forge new business approaches in the energy industry.

Paris Points the Way Forward on International Environmental Policy

By Beverly Barrett, Manager, UH Energy Advisory Board

Regardless of your views on climate change, it is unprecedented that nearly 200 nations came together in early December for the Conference of Parties and the 21st United Nations Framework Conference on Climate Change (UNFCCC), known as “COP21.”  This meeting also served as the conference of Parties to the Kyoto Protocol.

It was just the latest in a string of efforts to reach international consensus on climate policy. Twenty-one years ago, in March 1994, an earlier UNFCCC international environmental treaty was forged after negotiations at the 1992 Earth Summit in Rio de Janeiro.  This established the forum for future negotiations.

The most recent  conference focused on ambitious goals: to limit the rise in global average temperature to less than two degrees Celsius above pre-industrial levels and to achieve net zero annual emissions of greenhouse gases by the second half of this century.

Looking to 2050, it is clear that the victory is mostly symbolic. The agreement is not binding, and given political conflicts about these hotly debated topics, the commitments will not beratified by national legislatures. Domestic political support in many countries is not strong enough to ratify the negotiated measures.

Still, they are important, boosting efforts underway across the globe to reduce greenhouse gas emissions, including work here in the United States. The U.S. Congress continues to wrangle over Environmental Protection Agency (EPA) regulations that would limit emissions on coal-fired power plants. Natural gas or renewable energy technologies are suggested as alternatives but business planning and regulatory policy remain contentious.  Renewable energy – including wind and solar – will require additional technological innovation to become more widely used, including improvements to energy storage and transmission.

Historically, one of the most significant international environment pacts ratified by the U.S. legislature in recent decades was the Montreal Protocol. This international treaty to limit chlorofluorocarbons (CFCs), blamed for eroding ozone, was adopted by 46 countries, including the United States, and went into effect in 1987. A decade later, the Kyoto Protocol had nearly twice the national signatories. While the United States and China were noticeably absent from this agreement in Japan – the United States formally rejected the protocol in 2001 – the presence of both countries in Paris offered important evidence of a turning point and their renewed interest in leading the international dialogue on climate change policy.

The COP21 conference, which ran from November 30 to December 12, 2015, has been significant for three reasons:

  1. The spirit of cooperation, showing international solidarity after the tragic attacks in Paris on Nov. 13.
  2. The participation of China and the U.S. As the world’s two largest economies and the countries with the most carbon emissions, other nations have looked to these international giants for leadership on international environmental policy.
  3. Showing the way forward on international environmental policy in a new era of broad global participation.

Despite the prevailing optimism, there was not universal agreement at COP21, as world leaders split on a variety of issues. Nur Masripatin, lead negotiator for Indonesia, told the Financial Times that the deal was too weak. “The deal is not fair… but we don’t have more time, we have to agree on what we have now,” she said.

Supporters such as Prakash Javadekar, Minister of State for Environment, Forests and Climate Change in India, told the newspaper the action marked “a historic day. It is not only an agreement, but we have written a new chapter of hope in the lives of seven billion people on the planet.”

The U.S. lead negotiator, Secretary of State John Kerry, has praised the outcome as “a tremendous victory for all of our citizens.  . . . It is a victory for all of the planet and for future generations.  . . .  I know that all of us will be better off for the agreement we have finalized here today.”

In addition to its promises to reduce carbon emissions, the agreement pledged foreign aid to developing countries to support their move to more advanced electric generation sources including natural gas, wind and solar.

And the work continues. Morocco will host COP 22 next November in Marrakech. This meeting in North Africa will provide another opportunity for further commitments. In addition to providing progress reports on the goals presented in Paris, advocates will continue to press for the parties to adopt a binding treaty.

COP 21 has shown the way forward with nearly all of the globe’s nations embracing democratic principles to present their views on environmental policy. As the world becomes smaller, with enhanced communications and technologies, the commitment to cooperate on environmental policy becomes even more attractive. The Paris conference built a framework for our intentions to steward the environment while supporting energy sustainably that can show the way forward for climate change activists and skeptics alike. This is a unique opportunity for solidarity in international environmental policy.

 

Beverly Barrett is manager of the University of Houston’s Energy Advisory Board. She is a lecturer at the UH Hobby Center for Public Policy and the C.T. Bauer College of Business.

Stepping Up to Step Down Climate Change

By Nairah Hashmi, UH Energy Ambassador Fellow
Nairah is an undergraduate student majoring in chemical engineering.

Nairah-HashmiRecently, while browsing Snapchat Discover, I found an interesting article on climate change from the November 2015 issue of National Geographic. Although Snapchat is not the most conventional way of learning about the world, I did learn something: people should individually take responsibility for their impact on climate change, rather than wait Continue reading