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WHAT DOES NET-ZERO MEAN?

Posted on: February 25, 2020

 

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THIS POST IS A CRITICAL REVIEW OF THE “NET ZERO CLIMATE ACTION” PROCEDURE AS DESCRIBED IN THE SCIENCE OF CARBON BUDGETS DOCUMENT PUBLISHED BY AN ORGANIZATION CALLED “ENERGY AND CLIMATE INTELLIGENCE UNIT” (ECIU). THE REVIEW IS PRESENTED AS A SERIES OF CLAIMS MADE IN THE ECIU DOCUMENT WITH EACH CLAIM FOLLOWED BY A RESPONSE. THE FULL TEXT OF THE ECIU REPORT IS INCLUDED HERE AS A PDF DOCUMENT  NETZEROPDF

 

 

CLAIM: Net zero means that EMISSIONS are balanced by ABSORPTION of an equivalent amount from the atmosphere. Carbon Capture and Storage (BECCS) technology exists but it is not used because of cost and technical considerations. Therefore, “net” means net of natural photosynthesis, specifically additional natural photosynthesis that can be claimed in terms of specific action taken by humans (so that it can be described as human activity) in terms of things like reforestation and afforestation where the CO2 removal time span is in the order of 50 to 100 years. In countries where incremental afforestation and reforestation opportunities are limited this activity can be carried out overseas particularly in poor third world countries with poor forest management. A more lucrative option for claiming ownership  of CO2 removal by way of nature’s photosynthesis mechanism is the so called “blue carbon” found in shallow coastal waters in the equatorial region where underwater plants such as seagrass and mangrove remove CO2 from the atmosphere by photosynthesis and sequester the carbon for thousands of years [LINK] . The relevant issue in this regard is the degradation of coastal ecosystems and their blue carbon sequestration due to human activity [RELATED POST ON BLUE CARBON] . For this reason, additional carbon sequestration that can be attributed to action taken by humans to reduce coastal ecosystem degradation due to human activity can be claimed as CO2 removal in net emission accounting.

RESPONSE:  AGW climate change is a theory not about how changes in the carbon cycle change the rate of warming. Such changes are natural and predate the Industrial Revolution and they cannot be described as effects of the industrial economy. AGW climate change theory is about a warming trend attributed to the industrial economy and described as a perturbation of the carbon cycle by external carbon dug up by humans from under the ground where it had been sequestered from the carbon cycle for millions of years such that the external carbon is not part of the current account of the carbon cycle.

It is the injection of this external carbon by humans into the carbon cycle and the climate system that is identified by AGW climate change theory as the cause of the current warming. The carbon emission accounting for net emissions where carbon cycle flows and external artificial carbon flows are combined in simple addition and subtraction accounting is conceptually and mathematically flawed. The conceptual flaw is described above. The mathematical flaw is described in some detail a related post [LINK] .

Briefly, the issue is that carbon cycle flows are an order of magnitude larger than the fossil fuel emissions of humans but they cannot be directly measured. They must therefore be inferred. This is why the estimation of carbon cycle flows contains large uncertainties. It is shown in the related post [LINK]  that when these uncertainties are included in the flow accounting, the relatively smaller fossil fuel emissions cannot be detected because the flow account balances with and without fossil fuel emissions within the statistical range implied by the uncertainty in carbon cycle flows.

The implication of this result for “net zero climate action” strategies is that the accounting reduction in carbon cycle emissions must be shown to be statistically significant when the uncertainty in the relevant carbon cycle flows is taken into account.

In view of the result that the whole of the fossil fuel emissions is not detectable net of uncertainties in carbon cycle flows, it is highly unlikely that smaller changes to the carbon cycle that are assumed reduce net emissions will be found to be statistically significant when uncertainties are included in the accounting. In view of the arguments presented above, net zero climate action strategies, that is fossil fuel emissions net of projected reductions in carbon cycle flows, cannot be assumed to be less than fossil fuel emissions until it can be shown that the difference is statistically detectable net of uncertainties in carbon cycle flows. This important detail of net zero climate action strategies is missing from the flow accounting used in the net zero computation.

 

CLAIMThe science of ‘carbon budgets: Climate science is clear that to a close approximation, the eventual extent of global warming is proportional to the total amount of carbon dioxide that human activities add to the atmosphere.

 

RESPONSE: This claim is a reference to the proportionality between mean global surface temperature and cumulative emissions described by Damon Matthews and others since 2009. The strong correlation between temperature and cumulative emissions appears to support the validity of the regression coefficient for temperature against cumulative emissions that shows that cumulative emissions drive warming at the rate of somewhere between 1C and 2.5C of warming per teratonne of cumulative emissions. This coefficient is called the TCRE or Transient Climate Response to Cumulative Emissions. Climate action plans in terms of carbon budgets is computed based on the TCRE metric. Net zero climate action plans are designed in terms of the TCRE.

Yet, as shown in a related post [LINK] the strong proportionality between temperature and cumulative emissions found by climate scientists is a spurious correlation that has no interpretation in terms of phenomena in the real world. This implies that carbon budgets derived from the TCRE also have no interpretation in the real world [LINK] . It is this statistical flaw in the TCRE and not complexities of Earth System Models that explains the Remaining Carbon Budget problem in climate science [LINK]  {see also [LINK] }. The implication for Net Zero climate action plans is that the the net zero strategies that rely on the TCRE are illusory and the creation of a spurious correlation.

 

IN CONCLUSION, THE ANSWER TO THE QUESTION AT THE TOP OF THIS POST, “WHAT DOES NET ZERO MEAN?” IS THAT IT HAS NO INTERPRETATION IN TERMS OF CLIMATE ACTION AGAINST AGW CLIMATE CHANGE BECAUSE OF STATISTICAL WEAKNESSES IN ITS CONSTRUCTION THAT DOES NOT INCLUDE KNOWN LARGE UNCERTAINTIES IN CARBON CYCLE FLOWS AND THAT RELIES ON A SPURIOUS CORRELATION IN TERMS OF THE TCRE METRIC USED TO RELATE WARMING TO CUMULATIVE EMISSIONS. 

 

 

 

 

 

Other parts parts of the ECIU document are included below for reference: 

Net zero: why is it necessary? A number of countries including the UK are making commitments to move to a net zero emissions economy. This is in response to climate science showing that in order to halt climate change, carbon emissions have to stop – reducing them is not sufficient. ‘Net zero’ means that any emissions are balanced by absorbing an equivalent amount from the atmosphere. In order to meet the global warming target in the Paris Agreement, global carbon emissions should reach net zero around mid-century. For developed nations such as the UK, the date may need to be earlier. Some have already set such dates.

The science of ‘carbon budgets: Climate science is clear that to a close approximation, the eventual extent of global warming is proportional to the total amount of carbon dioxide that human activities add to the atmosphere. So, in order to stabilise climate change, CO2 emissions need to fall to zero. The longer it takes to do so, the more the climate will change. Emissions of other greenhouse gases also need to be constrained. In the Paris Agreement, governments agreed to keep global warming ‘well below’ 2 degrees Celsius, and to ‘make efforts’ to keep it below 1.5ºC. The Intergovernmental Panel on Climate Change (IPCC) released a report in October 2018 on the 1.5ºC target; it concluded that global emissions need to reach net zero around mid-century to give a reasonable chance of limiting warming to 1.5ºC.

Why ‘net zero’?

In many sectors of the economy, technologies exist that can bring emissions to zero. In electricity, it can be done using renewable and nuclear generation. A transport system that runs on electricity or hydrogen, well-insulated homes and industrial processes based on electricity rather than gas can all help to bring sectoral emissions to absolute zero.

However, in industries such as aviation the technological options are limited; in agriculture too it is highly unlikely that emissions will be brought to zero. Therefore some emissions from these sectors will likely remain; and in order to offset these, an equivalent amount of CO2 will need to be taken out of the atmosphere – negative emissions. Thus the target becomes ‘net zero’ for the economy as a whole. The term ‘carbon neutrality’ is also used.

Sometimes a net zero target is expressed in terms of greenhouse gas emissions overall, sometimes of CO2 only. The UK Climate Change Act now expresses its net zero emissions target by 2050 in terms of greenhouse gases overall.

Negative emissions

The only greenhouse gas that can easily be absorbed from the atmosphere is carbon dioxide. There are two basic approaches to extracting it: by stimulating nature to absorb more, and by building technology that does the job.

Reforestation
Increasing forest cover can help absorb carbon dioxide emissions. Image: Jon Sullivan, creative commons licence
Plants absorb CO2 as they grow, through photosynthesis. Therefore, all other things being equal, having more plants growing, or having plants growing faster, will remove more from the atmosphere. Two of the easiest and most effective approaches for negative emissions, then, are afforestation – planting more forest – and reforestation – replacing forest that has been lost or thinned. Technical options include BioEnergy with Carbon Capture and Storage (BECCS) (see our Negative Emissions briefing.)

Who is moving to net zero?

A number of countries have already set targets, or committed to do so, for reaching net zero emissions on timescales compatible with the Paris Agreement temperature goals. They include the UK, France, Spain, Denmark, Portugal, New Zealand, Chile, Costa Rica (2050), Sweden (2045), Iceland (2040), Finland (2035) and Norway (2030). The tiny Himalayan Kingdom of Bhutan and the most forested country on earth, Suriname, are already carbon-negative – they absorb more CO2 than they emit.

In addition, the European Union recently agreed measures that are likely to result in the bloc adopting a net zero target by 2050 at the latest.

The principle that rich nations should lead on climate change is enshrined in the UN climate convention that dates back to 1992, and was reconfirmed in the Paris Agreement. Therefore, if the science says ‘global net zero by mid-century’, there is a strong moral case for developed countries adopting an earlier date.

So far, the UK, France, Sweden and Norway have enshrined their net zero targets in national law. Other nations including Spain, Denmark, Chile and New Zealand are looking to do so.

Interim Minister of State for Energy and Clean Growth Chris Skidmore
Chris Skidmore, Interim Minister of State for Energy and Clean Growth, signs legislation to commit the UK to a legally binding target of net zero emissions by 2050. Image: Gov.uk
In the UK

Immediately after the IPCC published its Special Report on 1.5°C in October 2018, the governments of the UK, Scotland and Wales asked its official advisers, the Committee on Climate Change (CCC), to provide advice on the UK and Devolved Administrations’ long-term targets for greenhouse gas emissions.

The CCC had previously indicated that the UK should be aiming for net zero emissions by 2045-2050 in order to be compatible with the 1.5ºC Paris Agreement goal.

The CCC delivered its advice in May 2019. Its high-level recommendations were:

For the UK, a new target: net-zero greenhouse gases by 2050 (up from the existing emissions reductions target of 80% from 1990 levels by 2050);
For Scotland, a net-zero date of 2045, ‘reflecting Scotland’s greater relative capacity to remove emissions than the UK as a whole’;
For Wales, a 95% reduction in greenhouse gases by 2050, reflecting it having ‘less opportunity for CO2 storage and relatively high agricultural emissions that are hard to reduce’.
The governments of Wales and Scotland swiftly accepted the CCC’s advice, and on 12 June 2019, the UK government laid a statutory instrument to amend the 80% target in the Climate Change Act 2008. Just over two weeks later, the new net zero target (100% from 1990 levels by 2050) was formally signed into law.

Only a matter of days before France could complete the feat, the UK had pipped them to it and become the first G7 country to legislate for net zero greenhouse gas emissions by 2050.

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