The Enormous Significance For Climate Law and Ethics Of a Dutch Court’s Order Requiring the Netherlands To Reduce Its GHG Emissions by 25% by 2020



In June, a Dutch court in the landmark Urgenda decision concluded that the Netherlands must reduce its ghg emissions by 25% below 1990 levels by 2020.  This is the first case in the world where a national government has been ordered by a court to reduce its greenhouse gas (ghg) emissions commitments by a specific amount on the basis that its current commitments and polices are not legally sufficient. This case had enormous potential significance not only for climate change law but also for ethical arguments made about what a nation should do to reduce its ghg emissions if the case for one reason or another is not directly applicable to legal responsibilities of nations other than the Netherlands.

Although the court’s decision on the Netherlands’ emissions reductions has been widely publicized around the world, the logic that the court used to conclude that the Dutch government had a duty to reduce its ghg emissions by 25% below 1990 by 2025 has received little media attention despite the fact that much of the court’s reasoning is potentially legally applicable to the responsibility of all other developed nations. And so, the reasoning in the Urgenda case could be used by proponents of stronger responses to climate change in other countries. Yet, as we will explain in this post, despite the fact if other courts apply the reasoning in the Urgenda to other developed nations, many developed nations including the United States, Australia, Canada, and New Zealand would be required to increase their national ghg emissions commitments or INDCs, recent science on how much ghg concentrations in the atmosphere can rise without causing dangerous climate change supports the conclusion that the Dutch court mandated ghg emissions reductions target of -25% below 1990 levels by 2020 is  still not stringent enough.

Much of the Court’s logic in its decision is relevant to the ethical issues that nations must face in developing climate change policy, even if the court’s reasoning in the Urgenda case is not directly legally applicable in other countries, After identifying the court’s legal reasoning in the bulleted paragraphs below, the significance of the legal reasoning for climate change ethics is identified in italics.

This post first reviews the Dutch Court’s logic that is relevant to how other nations should determine their ghg emissions reduction commitments under the UNFCCC, or INDCs. This is followed by a brief comment on the significance of the legal reasoning for climate change ethics.

II. The Urgenda court’s logic and its ethical significance.

Although the Dutch court relied in part on Dutch law to reach its decision which is not likely relevant to other developed nations, In reaching its decision that the Netherlands must reduce its ghg emissions by 25% below 1990 levels by 2020 and 40% below 1990 levels by 2030, the court relied upon the following legal reasoning which could be followed by other developed nations:

  • ALL developed parties agreed at the Cancun COP in 2010 to act with a view to reducing global greenhouse gas emissions so as to hold the increase in global average temperature below 2°C above pre-industrial levels, and that Parties should take urgent action to meet this long-term goal on the basis of equity.

This is grounds for the conclusion that nations have an ethical duty, even if the legal promise cannot be enforced, to adopt policies that will reduce their ghg  emissions to the nation’s fair share of global emissions that at a minimum are sufficient to limit warming to 2°C. Yet, because temperature increases below 2°C will impose harsh impacts on vulnerable people and nations, an ethical argument can be made that nations have an ethical duty to do whatever they can to limit any further warming. Particularly because there is scientific concern that warming of less than 2°C may trigger the catastrophic warming that the 2°C warming limit was designed to protect against, there is a strong ethical argument that nations need to do more than adopt policies that would allow warming to 2°C. 

  • The court relied upon the 2007 IPCC’s 4th Assessment report including conclusions to achieve a goal of limiting warming limit of 2 °C, ghg atmospheric concentrations stabilized at 450 ppm CO2 would create a  50% chance of preventing warming greater than the 2 °C warming limit.

As above, nations have a clear ethical duty, at the very minimum, to adopt policies that, working with other nations, will limit atmospheric concentrations of 450 ppm. Yet, as we will see below, stabilizing atmospheric ghg concentration at 450 ppm is likely not stringent enough to keep warming within 2°C not to mention that a more protective warming limit of perhaps 1.5 °C may be s needed to prevent catastrophic warming. Every national INDC is implicitly a position on what level of atmospheric ghg concentrations the nation is seeking to achieve in establishing an INDC and its fair share of global emissions the nation has committed to in selecting the INDC. 

  • The IPCC concluded to stabilize ghg emissions at 450 ppm, Annex 1 countries must reduce ghg emissions by -25% to -40% below 1990 levels by 2020 and -80% to 95% below 1990 levels by 2050.

All developed nations have both a legal and ethical duty to reduce their ghg emissions by a minimum of 25% by 2020 below 1990 levels but because the 450 ppm atmospheric concentration goal is not likely protective enough, the national commitments of developed countries must be greater than -25% below 1990 by 2020.   .

  • In identifying the -25% to -40% reduction range by 2020, the IPCC relied upon a study which examined different approaches to apportioning emissions between regions.

One way of resolving conflicts between equity frameworks is to deduce emissions reduction target levels by considering multiple equity frameworks that pass ethical scrutiny and averaging them. 

  • Several provisions of the UNFCCC have been agreed to by all nations including provisions in which nations agreed to: (a) under art. 2 of the UNFCCC  to adopt policies and measures that will lead to “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system,” (b) under art. 3 of the UNFCCC to protect the climate system for the benefit of present and future generations of humankind, on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities and accordingly, the developed country parties should take the lead in combating climate change and the adverse effects thereof,  (c ) to take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects and where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures.

Although it is not news to either lawyers or ethicists that nations have duties to adopt policies that will prevent dangerous climate change, to protect the climate for the benefit of future generations, to apply precautionary measures in developing climate policies, and that developed countries should take the lead in reducing the threat of climate change, this decision is the first legal decision to apply these principles to a national ghg emissions target. A strong argument can be made that nations have ethical duties to abide by these provisions in the UNFCCC on the basis of many ethical arguments including that nations have agreed to be bound by these provisions and nations should not break their promises..

  • Climate science leads to the conclusion that national climate strategies that achieve ghg reductions sooner rather than later are preferable because later-action scenarios pose greater risks of harsh climate impacts for four reasons:
    • First delaying action allows more greenhouse gases to build-up in the atmosphere in the near term, thereby increasing the risk that later emission reductions will be unable to compensate for this build up.
    • Second, the risk of overshooting climate targets for both atmospheric concentrations of greenhouse gases and global temperature increase is higher with later-action scenarios.
    • Third, the near-term rate of temperature is higher, which implies greater near-term climate impacts.
    • Lastly, when action is delayed, options to achieve stringent levels of climate protection are increasingly lost.”

This part of the decision is of great ethical importance because it interpreted various provisions of the UNFCCC to require nations to adopt climate policies that achieve ghg emissions sooner  rather than later. In doing this the court relied in part on an interpretation of the precautionary principle which has been rarely used for requiring nations to act quickly. Most commentators on the precautionary principle have used it to support arguments that nations may not use scientific uncertainty as an excuse for insufficient action. Yet the Urgenda court used the precautionary principle to conclude that this principle required action sooner rather than later because delay increased the risk of catastrophic climate impacts. 

  • The Dutch government’s argument that it should not be required to make major reductions because the Netherlands is only 0.5 % of global reductions and therefore its reductions will not affect global emissions because all nations have a global responsibility and a responsibility to take precautionary measures, nations have both an individual and joint responsibility.

This part of the decision is consistent with the ethical conclusion that all nations have ethical and moral duties to reduce their emissions to their fair share of safe global emissions without regard to the size of the nation. 

  • Article 21 of the Dutch Constitution requires Dutch authorities to keep the country habitable and to protect and improve the environment and imposes a duty of care on the State relating to the livability of the country and the protection and improvement of the living environment.

Although this conclusion is based on a provision of Dutch law, the legal reasoning supports the ethical conclusion that nations have a moral duty to protect the environment for the benefit of the nation’s citizens.

  • The Parties agree that due to the current climate change and the threat of further change with irreversible and serious consequences for man and the environment, the State should take precautionary measures for its citizens.

Although the precautionary principle is derivable from ethical reasoning, the decision supports the conclusion that the precautionary principle is binding on nations because they have promised to apply it. 

  • Since it is an established fact that the current global emissions and reduction targets of the signatories to the UN Climate Change Convention are insufficient to achieve the 2° warming limit and thus the chances of dangerous climate change should be considered as very high – and this with serious consequences for man and the environment, both in the Netherlands and abroad – the State is obliged to take measures in its own territory to prevent dangerous climate change (mitigation measures). Since it is also an established fact that without far reaching reduction measures, the global greenhouse gas emissions will have reached a level in several years, around 2030, that achieving  the 2°C warming limit will have become impossible, these mitigation measures should be taken expeditiously.

This legal reasoning also supports the ethical conclusion that nations must not only act ambitiously to reduce the threat of climate change but must also act quickly and rapidly. 

  • The State has argued that allowing Urgenda’s claim, which is aimed at a higher reduction of greenhouse gas emission in the Netherlands, would not be effective on a global scale, as such a target would result in a very minor, if not negligible, reduction of global greenhouse gas emissions. After all, whether or not the 2°C target is achieved will mainly depend on the reduction targets of other countries with high emissions. More specifically, the States relies on the fact that the Dutch contribution to worldwide emissions is currently only 0.5%. If the reduction target of -25% to -40% from Urgenda’s claim were met the State argues that this would result in an additional reduction of 23.75 to 49.32 Mt CO2-eq (up to 2020), representing only 0.04-0.09% of global emissions. Starting from theidea that this additional reduction would hardly affect global emissions, the State argues that Urgenda has no interest in an allowance of its claim for additional reduction. This argument does not succeed. It is an established fact that climate change is a global problem and therefore requires global accountability. The fact that the amount of the Dutch emissions is small compared to other countries does not affect the obligation to take precautionary measures in view of the State’s obligation to exercise care. After all, it has been established that any anthropogenic greenhouse gas emission, no matter how minor, contributes to an increase of CO2 levels in the atmosphere and therefore to hazardous climate change. Emission reduction therefore concerns both a joint and individual responsibility of the signatories to the UN Climate Change Convention. In view of the fact that the Dutch emission reduction is determined by the State, it may not reject possible liability by stating that its contribution is minor. The court arrives at the opinion that the single circumstance that the Dutch emissions only constitute a minor contribution to global emissions does not alter the State’s obligation to exercise care towards third parties. Here too, the court takes into account that in view of a fair distribution the Netherlands, like the other Annex I countries, has taken the lead in taking mitigation measures and has therefore committed to a more than proportionte contribution to reduction. Moreover, it is beyond dispute that the Dutch per capita emissions are one of the highest in the world.

This is a very significant conclusion for climate ethics because many opponents of climate change polices have successfully argued that nations have no duty to act until large emitters like China and India act. The decision is very clear in explaining why such an argument is legally indefensible and also ethically unsupportable in light of the fact that climate change is a global problem and requires global responsibility, any anthropogenic ghg emission, no matter how minor, contributes to an increase of CO2 levels in the atmosphere and therefore to hazardous climate change, and emission reductions entail both a joint and individual responsibility of nations to act.

  • Urgenda is correct in arguing that the postponement of mitigation efforts, as currently supported by the State (less strict reduction between the present day and 2030 and a significant reduction as of 2030), will cause a cumulation effect, which will result in higher levels of CO2 in the atmosphere in comparison to a more even procentual or linear decrease of emissions starting today. A higher reduction target for 2020 (40%, 30% or 25%) will cause lower total, cumulated greenhouse gas emissions across a longer period of time in comparison with the target of less than 20% chosen by theState. The court agrees with Urgenda that by choosing this reduction path, even though it is also aimed at realising the 2°C target, will in fact make significant contributions to the risk of hazardous climate change and can therefore not be deemed as a sufficient and acceptable alternative to the scientifically proven and acknowledged higher reduction path of -25% to -40% in 2020.

This part of the opinion also confirms the ethical conclusion that higher and quicker ghg emissions reduction targets are ethically required  because slower, less ambitious targets will make the problem worse. 

  • In the opinion of the court, the possibility of damages for those whose interests Urgenda represents, including current and future generations of Dutch nationals, is so great and concrete that given its duty of care, the State must make an adequate contribution, greater than its current contribution, to prevent hazardous climate change.

This part of the decision reiterates the conclusion that nations have an ethical duty to its citizens to prevent dangerous climate change. The court in another part of the decision also concluded that nations have a clear legal duty to not harm people outside of its jurisdiction under the “no harm” rule which is both expressly referenced in the UNFCCC and is customary international law but decided this clear duty was not relevant to the Urgenda case because the Urgenda plaintiffs were Danish nationals. 

III. Recent Scientific Conclusions in Regard to the Adequacy of the 450 ppm atmospheric Goal  

As we have seen, the Urgenda decision relied on the 2007 IPCC report on what emissions reductions would be required to limit warming to tolerable limits which assumed that 2°C2 was a reasonable warming limit for the world and that a 450 ppm CO2 atmospheric concentration was a reasonable atmospheric concentration target to give reasonable chance of keeping warming from exceeding the 2 degree C warming limit that has been agreed to by the international community.  Since then several scientific reports have  been published that claim : (1) the -25%  to -45% reduction levels identified in the 2007 IPCC report are not stringent enough to live within a carbon budget that will protect the world from warming greater than 2°C, and (2) that the 2°C warming limit and the 450 ppm CO2 concentration goal are not stringent enough to prevent dangerous warming .

Climate Tracker Global Emissions Reduction Pathway Needed to Limit Warming to 2°C


A recent report by Climate Tracker summarized the most recent science on needed ghg reduction pathways to stay within the 2 degree C warming budget as follows:

Limiting warming below 2 degrees with a high chance means that total GHG emissions would need to be zero between 2060 and 2080 and likely negative thereafter CO2 emissions from fossil fuel combustion and industry would need to be zero by as early as 2045 and no later than 2065 and be negative thereafter.

Because total global emissions must be zero between 2060 and 2080, developed nations need to be zero before 2060. Since the 2007 IPCC on which the Urgenda decision was based called for developed nations to reduce their ghg emissions by -80% to -95% below 1990 by 2080, it is clear that emissions reductions called for in the Urgenda decision are now not sufficient to achieve the  2°C warming limit.

James Hansen recently issued an affidavit in support of litigation that has been intiated against the US state of Oregon which summarizes recent scientific views of many scientists in which he concluded that to protect against dangerous climate change, atmospheric CO2 must be brought down to 350 ppm and to achieve this the world needs to reduce ghg emissions by 6% per annum coupled with reforestation and improved forest and agricultural practices.

In this report, Dr. Hansen also claims that the required rate of emissions reduction would have been about 3.5% per year if reductions had started in 2005 and continued annually thereafter, while the required rate of reduction, if commenced in 2020, will be approximately 15% per year.

Applying these conclusions to the Urgenda decision leads to the conclusion that the Dutch court’s order requiring the Netherlands to reduce its emissions  by -25% below 1990 levels is not stringent enough to meet the Netherlands legal and ethical responsibilities to act to prevent dangerous climate change.


Donald A. Brown

Scholar In Residence and Professor

Sustainability Ethics and Law

Widener University Commonwealth Law School

The US Media’s Grave Communication Failure On The Magnitude Of GHG Emissions Reductions Necessary To Prevent Dangerous Climate Change

 I. Introduction

This is the third entry in a series that is examining grave communications failures of the US media in regard to climate change. In this series we examine how the American media has utterly failed to communicate to US citizens about five essential aspects of climate change that need to be understood to know why climate change is a civilization challenging problem that requires dramatic, aggressive, and urgent policy action to avoid harsh impacts to hundreds of millions of people around the world. has recently developed a video that summarizes these failures: Five Grave Communication Failures of US Media on Climate Change at:

This is the second paper that examines in more detail the issues briefly examined in the video. In the last entry we examined the failure of the US media to communicate about the nature of the strong scientific consensus about human-induced climate change. In this post we look at the failure of the US press to communicate about the enormous magnitude of greenhouse gas emissions reductions necessary to prevent harsh climate change impacts.

Subsequent posts will examine the following additional communication failures of the US media:

  •  The consistent barrier that the United States has been in developing a global solution on climate change for over 20 years.
  •  The fact that climate change must be understood as a civilization challenging ethical problem, an understanding that is of profound significance for climate change policy formation.
  •  The nature of the climate change disinformation campaign in the United States.

II. Communication Failures On The Magnitude Of The GHG Emissions Reductions Necessary To Prevent Dangerous Climate Change

 Most Americans are completely unaware of the magnitude of global greenhouse gas emissions reductions necessary to prevent dangerous climate change. If US citizens don’t understand the size and scope of the problem, they will almost certainly refuse to support legislation and policies necessary to put the United States on an emissions reduction pathway that represents the US fair share of safe global emissionsBecause, as we discussed in the last entry, the scientific consensus is so strong that the world is headed to harsh and dangerous impacts, the US media’s failure to communicate clearly about the magnitude of the problem facing the world is a serious, grave, and tragic lapse.

No US national climate change strategy makes any sense unless it is understood to implicitly be a position on the US fair share of a global greenhouse gas emissions reductions pathway capable of preventing dangerous climate change. Yet when US federal climate change legislation was under consideration between 2009 and 2010, there was almost no public discussion about whether proposed US climate change legislation would reduce US greenhouse gas emissions to levels that represent the US fair share of safe global emissions.

To understand the urgency for civilization challenging emissions reductions it is necessary to understand: (a) what temperature increases will likely trigger harsh climate change impacts,  (b) what atmospheric concentrations of greenhouse gases will cause specific temperature increases that are of concern, and (c) what quantities of greenhouse gas emissions will exceed atmospheric greenhouse target concentrations. Only then can one understand the amount of global greenhouse gas emissions reductions from business as usual that are necessary to avoid dangerous climate change.

A. Dangerous Temperature Increases

The international community agreed at a meeting of the conference of the parties under the United Nations Framework Convention on Climate Change in Copenhagen in 2009 that the world must work together to limit warming to an additional 2oC to avoid rapid non-linear impacts from climate change. The 2oC warming limit was agreed to because there is widespread agreement among the vast majority of mainstream scientists that warming of more than 2oC significantly increases the probability of harsh climate impacts.

However, catastrophic harms, at least for some parts of the world, could be triggered by additional warming of less than 2oC because there is uncertainty about how the Earth will respond to different increases in temperatures. (Athanasiou and Bear 2002) The 2oC upper temperature limit is quite controversial scientifically because, as we shall see, some scientists believe that lower amounts of additional warming could set into motion rapid climate changes that could greatly harm people around the world and increases of as little as 1oC will likely greatly harm some people in some regions.

A report, “Assessment of Knowledge on Impacts of Climate Change,” prepared by the Potsdam Institute to examine the meaning of “dangerous” climate change under the UNFCCC supported the 2°C danger limit after a rigorous analysis of climate change impacts at various temperatures concluding:

Above 2°C the risks increase very substantially involving potentially large extinctions or even ecosystem collapses, major increases in hunger and water shortage risks as well as socio-economic damages, particularly in developing countries. (Hare 2003: 89)

Yet, even this report identified very serious global and regional impacts below 2°C. In fact, this report concluded that temperature increases below 1°C threaten highly vulnerable ecosystems and between 1°C and 2 °C increase the risks of damage for all ecosystems and particularly for some regional ecosystems. (Hare 2003: 89)

There is substantial scientific evidence that even a 1.5°C temperature limit would not be sufficient to protect those most vulnerable to climate change. For instance, a recent paper by Jim Hansen and seven other authors concluded that additional warming should be limited to 1°C warming to prevent serious harms. (Hansen et al 2008) To do this, existing atmospheric concentrations of CO2 must not only not be allowed to rise the small amount to 450 ppm CO2 from current levels of 394 ppm CO2 but must be reduced below existing levels to 350 ppm CO2. (Hansen et al. 2008) According to this paper, the world has likely already shot past the level of atmospheric greenhouse gas concentrations that will lead to dangerous climate change for many. According to Hansen and his collaborators, the world has already used up all of the assimilative capacity of the atmosphere and biosphere that has been available to buffer against dangerous climate change. As a result, this paper asserts that to prevent dangerous climate change the world must not only reduce its emissions but reduce existing greenhouse gas CO2 atmospheric concentrations from the current 394 ppm to 350 ppm CO2 to avoid dangerous climate change.

And so, although the international community agreed in Copenhagen to limit future warming to 2°C, this could prove to be a limit that is too high to protect millions around the world. As one observer recently noted:

We feel compelled to note that even a “moderate” warming of 2°C stands a strong chance of provoking drought and storm responses that could challenge civilized society, leading potentially to the conflict and suffering that go with failed states and mass migrations. Global warming of 2°C would leave the Earth warmer than it has been in millions of years, a disruption of climate conditions that have been stable for longer than the history of human agriculture. Given the drought that already afflicts Australia, the crumbling of the sea ice in the Arctic, and the increasing storm damage after only 0.8 °C of warming so far, calling 2°C a danger limit seems to us pretty cavalier.

(Real Climate 2009)

In thinking about an upper temperature limit, many scientists are concerned with avoiding runaway climate change. That is, they fear that global temperatures will exceed a tipping point that will trigger a release of stored carbon from the biosphere, an event that would cause further rapid climate change. Runaway climate change would mean that governments would lose the ability to control future climate change that they would otherwise have through reducing greenhouse gas emissions from fossil fuel combustion and deforestation. That is, runaway climate change means that human action would be unable to stop significant temperature increase without massive geo-engineering. (Washington and Cook 2011: 30-31) This is so because, among other things, there are vast amounts of methane stored in permafrost, methane hydrates on the ocean floor, and carbon in the forests that could be released as the world warms. If the world warms too much, increased temperatures could cause huge amounts of carbon to be released that would overwhelm the quantities of carbon being released through fossil fuel combustion and deforestation. This is known to be a possibility, because such releases of stored carbon have happened in Earth’s history and caused rapid non-linear Earth temperature changes.

And so, the magnitude of greenhouse gas reductions needed to prevent dangerous climate change is understood to be the reductions from business-as-usual that will allow atmospheric concentrations of greenhouse gases to be stabilized at levels that will limit warming to between 1 to 2°C with prudence calling for a 1°C limit. We now turn to what atmospheric greenhouse gas atmospheric concentrations levels are understood to prevent warming above these amounts.

B. Atmospheric Greenhouse Gas Stabilization Goal

The amount of warming that will be experienced from different greenhouse gas atmospheric concentrations is usually referred to as the issue of “climate sensitivity.” Climate sensitivity is somewhat uncertain as there are remaining scientific uncertainties about the magnitude of the positive and negative feedbacks in the climate system.

Climate sensitivity is usually defined to mean the amount of warming that the Earth will experience if atmospheric concentrations of COreach 560 ppm of COequivalent, where COequivalent is the metric which translates other greenhouse gases into an equivalent level of CO2 . The IPCC in its Fourth Assessment Report (AR4) concluded that climate sensitivity is likely to be in the range 2 to 4.5 °C with a best estimate of about 3°C, and is very unlikely to be less than 1.5 °C. (IPCC 2007) The IPCC also noted that climate sensitivity values substantially higher than 4.5 °C cannot be excluded. And so the temperature change that the consensus view believes is likely if all of the greenhouse gases rise to 560 ppm carbon equivalent is somewhere between 2 °C and 4.5 °C with even higher temperatures possible. The current concentration of CO2 is 394 ppm. (CO2  Now 2012)

To operationalize an upper temperature limit, the international community must set an atmospheric greenhouse gas concentration stabilization limit. Since there is scientific uncertainty about how much warming will be experienced by different atmospheric greenhouse gas concentration levels, there is significant scientific controversy about what the greenhouse gas atmospheric stabilization target should be to achieve any warming limit.

Making the calculation of emissions reductions needed at any one time is complicated by the fact that how rapidly greenhouse gas emissions must be reduced is a problem that depends upon when global emissions reductions begin. The longer the international community waits to reduce greenhouse gas emissions, the steeper the necessary emissions reductions pathway becomes. It is relatively easy to calculate the amount of additional tons of emissions that can be allowed to stabilize atmospheric concentrations at a certain level such as 450 ppm CO2 but this number will depend upon when emissions reductions begin. At any time it is therefore possible to create a budget that identifies the total tons of emissions that can be allowed before a specific atmosphere concentration is exceeded but the longer the international community waits to begin to reduce emissions, the steeper the reductions must be.

The magnitude of the challenge entailed by the need to set a greenhouse gas atmospheric concentration target becomes evident after looking at the probability of exceeding 2°C if CO2 equivalent targets are set at specific levels such as 450 or 550 ppm. In the following chart the colored lines represent emissions reduction pathways that would stabilize atmospheric concentrations of carbon dioxide equivalents at various levels. The yellow line is a pathway that would stabilize at 550 ppm. The red line is a reduction pathway that could stabilize carbon dioxide equivalent at 450 ppm. The numbers on the boxes on these two lines specify the probability of exceeding 2°C if atmospheric concentration levels are stabilized at these levels.

From this chart we therefore see that if atmospheric carbon dioxide is stabilized at 550 ppm there is between a 75% and 99% chance that the world will experience temperatures in excess of 2°C. Looking at the red line we see that even at a stabilization level of 450 ppm there is between a 45% and 86% chance that the world experience increases in temperature greater than 2°C. Because CO2 levels are already approaching 395 ppm and other greenhouse gases make current carbon dioxide equivalent levels in the vicinity of 430 ppm it becomes evident that the world is running out of time to stabilize atmospheric carbon dioxide levels in the atmospheric concentrations that would limit warming to 2°C. Because as we have seen it is possible that temperature increases as small as 1°C will create harsh impacts for some people in some parts of the world it becomes apparent that the need to reduce greenhouse gases aggressively, and dramatically, and urgently.

C. Percentage Reductions From Business As Usual Required To Stabilize Atmospheric Concentrations Of Greenhouse Gases

The startling magnitude of the challenge to the world from climate change becomes apparent upon reflection that the world is currently increasing greenhouse gas emissions  during the last decade of an average annual increase of 2.7%. (PBL 2012) Yet to stabilize carbon dioxide concentrations at about 450 ppm by 2050, global emissions will have to decline by about 60% from current levels. (Hossol 2011).  Because developing countries need to expand economic activity to escape grinding poverty according to one US White House paper, industrial countries greenhouse gas emissions would have to decline by about 80% by 2050. (Hossol 2011)

Given that greenhouse emissions are increasing year to year and that the entire world will need to reduce emissions by as much as 60% by 2050 to give any hope of remaining below 2°C, the challenge to the world is staggering. One observer sums up the situation as following:

The growth of emissions is making the task ahead more and more difficult. The longer we wait to start shrinking emissions, the faster we’ll have to shrink them to stay under budget. Here’s a visualization of what that means — some sample reduction curves with varying peak years (the four different lines are based on the four main IPCC scenarios):

(citing Anderson, K.  2011)

As you can see, if we delay the global emissions peak until 2025, we pretty much have to drop off a cliff afterwards to avoid 2 degrees C. Short of a meteor strike that shuts down industrial civilization, that’s unlikely.

This, then, is the brutal logic of climate change: With immediate, concerted action at global scale, we have a slim chance to halt climate change at the extremely dangerous level of 2°C. If we delay even a decade — waiting for better technology or a more amenable political situation or whatever — we will have no chance.

(Roberts 2011)

Although the challenge of achieving sufficient global greenhouse gas emissions to prevent 2°C is extraordinarily daunting, as we have explained above a 2°C warming limit may not prevent catastrophic harm because temperature increases more than 1°C may cause great harm.

International climate negotiations have sought to find a global solution to climate change since they began in 1990 and have struggled since then to reach a global deal among most countries to prevent dangerous climate change. Because global emissions continue to rise rather than decrease after 20 years since climate change negotiations began, the international community has lost several decades in finding a way to prevent dangerous climate change. And so, the human race may be running out of time to prevent dangerous climate change. Yet most Americans are unaware of the seriousness and urgency of the staggering problem we are facing. The US media has utterly failed to sound the alarm about the magnitude of the threat of climate change.


Anderson, Kevin (2011)  Going Beyond Dangerous Climate Change,

 Athanasiou, T. and Bear, P. (2002), Dead Heat: Global Justice and Global Warming, Westminster, MD: Seven Stories Press, Canada.

CO2Now (2012)  Earth’s CO2 Now Home Page (March 2012).

Hansen. J., Sato, M., Kharecha, P., Beerling, Masson-Delmotte, V., Pagani, M., Raymo, M., Royer, D., Zachos, J. (2008)  Where Should Humanity Aim?

Hare, W. (2003)  Assessment Of Knowledge On Impacts Of Climate Change – ‘Contribution To The Specification Of Art’, 2 of the UNFCCC, Berlin: Potsdam Institute for Climate Research,

Hossol, Susan Joy (2011)  Emissions Reductions Needed To Stabilize Climate, Presidential Climate Project,

Intergovernmental Panel on Climate Change (IPCC) (2001) this multi-volume work was published as: (i) Climate Change 2001: Synthesis Report; (ii) Climate Change 2001: The Scientific Basis; (iii) Climate Change 2001: Impacts, Adaptation & Vulnerability; (iv) Climate Change 2001: Mitigation, Geneva, Switzerland: Intergovernmental Panel on Climate Change.

Intergovernmental Panel on Climate Change (IPCC) (2007) Climate Sensitivity And Feedbacks, in Pachauri, R., and Reisinger, A. (eds) Climate Change 2007: Synthesis Report, Contribution of Working Groups I, II, and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Geneva, Switzerland: Intergovernmental Panel on Climate Change, Available at:

PBL, Netherlands Environmental Assessment Agency (2012) Trends in Global Co2 Emissions, 2012 Report.

Real Climate (2009) Hit the Brakes Hard,

Roberts, David  (2011) The Brutal Logic Of Climate Change,

 Washington, H. and J. Cook (2011) Climate Change Denial: Heads in the Sand, by Climate Change Denial: Heads in the Sand, Earthscan, London and Washington


Donald A. Brown

Scholar In Residence

Sustainability Ethics and Law

Widener University School of Law