Friday, September 21, 2018


Understanding Time Lags Important for Climate Policies.

“Cumulative carbon”, the fact that human emissions of CO2 are removed only slowly from the atmosphere through the natural carbon cycle, is the essence of the climate change problem. Given the thermal inertia of our planet it may produce a substantial time lag between effective action, to limit emissions, and actual stabilisation of temperatures, equivalent to the operation of a domestic heating radiator on a one way ratchet. Some climate scientists believe this effect may have been exaggerated, and will be largely offset by other elements in the natural cycle. Even so there is a consensus that we need to move to a world of net zero emissions and beyond.

So much of the predictive element of climate science has been borne out by observation that it is easy to forget there are still major gaps in our understanding and major uncertainties that are very relevant to understanding what climate policies are necessary to (ultimately) stabilise global temperatures.

The slow but seemingly relentless upward trend in global surface temperatures sits firmly in the middle of past model predictions, and denials that it is actually happening (the famous Lawson “hiatus” based on cherry picking outlier el Nino effects), or that it has nothing to do with human contributions to greenhouse gas concentrations, look increasingly threadbare and ridiculous. There is no doubt that human-induced climate change is with us, and that it is dangerous.

However, although the science makes it clear that urgent emission reductions are essential, it is much less clear how much leeway we have, and whether the 1.5o C or 2.0o C “targets” are attainable. The uncertainties manifest themselves in discussions over the time lags involved, for example between stabilisation of the atmospheric concentration levels of CO2 and stabilisation of global temperature. These questions relate in turn to complexities of the natural carbon cycle and the

The issue of time lags is in some ways politically important. Thomas Stocker, then co-chairman of the IPCC Working Group I (assessing scientific aspects of the climate system and climate change), and addressing the Environmental Change Institute in Oxford in 2014, argued that “committed peak warming rises 3 to 8 times faster than observed warming”. The implication is that there are very substantial time lags. In this case temperatures could continue to rise, perhaps for several decades or even centuries, even if net human emissions were reduced to zero. Similar comments can be found from other climate scientists. It has even been suggested that the thermal inertia effect, considered on its own, could stretch the lag to about 200 years – the time for heat equilibrium adjustment to reach the deep oceans.

The intuitive physical explanation of long time lags is simply the phenomenon of thermal inertia. When we turn up the radiator at home it may take an hour or more for the room to reach a new equilibrium temperature. Global warming, in this analogy, is a radiator heating system on an upward ratchet. The issue for humanity is that by the time temperatures become really uncomfortable, we have already ratcheted up the future temperature to which we have committed. If this is a real danger it dramatically increases the risks associated with climate inaction or “business as usual” trends. It is also creates an alarming image of climate change as a kind of doomsday machine in which humanity is trapped through its failure to anticipate and respond.

However rather more optimistic views have been presented by other scientists. In 2014 Ricke and Caldeira[1] argued that the lags had been seriously overstated, suggesting a time lag of only ten years as a more appropriate estimate. Oxford-based climate scientists, such as Myles Allen, have also suggested that stabilising atmospheric concentrations could lead to a comparatively early stabilisation of global temperature.

The main reason is the potential offsetting effect of the absorption of incremental carbon through the various elements of the natural carbon cycle, including ocean CO2 uptake and the behaviour of biosphere carbon sinks. However there is no natural law that requires such a balance of effects, and the reality seems to be that we are trying to compare two magnitudes, both of which are of major importance but are also difficult to measure with precision. If the effects broadly cancel out over particular timescales, this is essentially a numerical coincidence within the modelling effort. We can expect future research, better measurement, and associated modelling, will gradually improve our understanding.

But melting ice caps are a separate story!

The above discussion does not however cover all the long time lags involved. One particular concern has to be the polar ice caps. If global temperatures reach the point where these start to melt, then the consequential effects in the form of rising sea levels will go on for centuries. Ice sheets, as opposed to sea ice, can, like the retreating glaciers, only be restored by precipitation. That will be slow and net annual ice gain will probably depend on conditions associated with a fall in global and polar temperatures to or beyond what used to be regarded as normal.

And the policy implications of these uncertainties?

In reality the consequences for policy of differing estimates can be exaggerated, since there is agreement on most fundamentals. Most modelling now recognises that stabilisation of temperature, even at a higher level, requires progress to net zero human emissions. Importantly, this is probably unachievable without substantial measures to remove CO2 (and other gases) from the atmosphere.  In practice processes for carbon sequestration are likely to be very expensive process. They represent a form of geo-engineering.

Monday, September 17, 2018


The Guardian two weeks ago featured an anguished reader’s letter concerned about the invasion of privacy involved in the installation of smart meters in UK households. It’s worth reflecting briefly on what the privacy and security issues might be, what the real social value of smart meters might be, and how we should balance these with an effective policy.

Smart meters, and I have just acquired one for my electricity supply, will tell you a number of things that you might have found it difficult to work out previously. These may include for example what your power use (in watts or kilowatts) is at any instant in time, what it was in the last few hours, days or months. The privacy concern is that the utility, your supplier, can be assumed to have the capability to collect and keep this data, and, for example, could build up a picture of the minute by minute electricity consumption of every household with a smart meter.

There are many, not particularly sinister, reasons why utilities might want to do this. At a minimum it can provide a better understanding of how consumers use electricity can help in planning future system needs, make sure that local networks have adequate capacity to cope with fluctuations in load, and so on.

On privacy and security issues we should perhaps be far more worried about the amount of sensitive information held on you by your bank and your credit or store card issuer, not to mention Facebook, Google and your telecoms supplier, or, and, currently in the news, the airlines you use. Between them these have tons of information about your shopping habits, lifestyle, opinions, financial affairs, favourite websites, and so on, all of which, if privacy and security are breached, potentially give rise to much more serious abuses than someone being able to work out what time a household has breakfast or runs the washing machine.

It’s also certainly true, as a number of readers are testifying, that the government has not fully thought through its policy objectives on smart meters, and that the programme is unlikely to deliver many of the promised benefits, at least in the short term. And of course there are as usual a lot of horror stories on installation failures. But none of this should blind us to the fact that there is a huge and essential future for devices which create a much closer connection between the way we use energy, and electricity in particular, and the factors that constrain when and how it is produced and delivered.

Let us take a simple future example. We expect a big future for electric vehicles. This has the potential to create big spikes in load, with everyone switching on together, in a period when we will depend increasingly on renewable energy sources which are much more variable than currently, and harder to match to varying consumer demand. One answer to this is for some EV owners to charge their vehicles overnight, but for the timing of that supply to be at the discretion of the supplier, who can match it to when production is available to meet it. In exchange for this surrender of direct control, consumers will get a much more favourable tariff for their EVs, and the practical issues of managing network overload, when all EV owners try to re-charge their vehicles immediately on return from work, can be avoided. This obviously implies an element of intrusion, in the sense that the utility “knows” the purpose of the load it is required to meet. It also assigns a choice (over timing) from the consumer to the utility. But this is a commercial transaction, willingly entered on both sides, providing benefits to both parties.

Smart meters are just a starting point for more sophisticated and user friendly tariff and conditions of use arrangements which can redefine the ways we use energy. No doubt there will be privacy issues to be managed, but essentially these will be no different in character from the privacy issues we encounter in relation to almost all our transactions with businesses large and small. They will be substantially less than most of those that we face in relation to financial transactions, social media and our day to day use of IT and the internet..

Some of the benefits that can flow from more sophisticated metering and tariffs are highlighted in a report published last week by Energy Systems Catapult, which starts to explore the numerous tariff issues highlighted by progress towards a low carbon economy.