David Hone

Through 2010 and 2011 in particular, weather extremes seemed to dominate the headlines. Extreme drought, rainfall, flood and wind all played a role in making the period one of the most expensive in terms of damage to infrastructure. In some locations there was also significant loss of life. It was also a time that saw the subject of extreme weather events rise up the climate change agenda, with numerous academic papers, blogs, seminars and campaigns focused on the issue.

Certainly as the atmosphere moves from one steady state to (presumably) another and one which is warmer and therefore has more energy, weather volatility should increase, at least during the period of transition. This is true in any control system where there is a change in set point (not exactly what is happening in the world, but analogous). The picture below is fairly typical, with large swings in response as the system adjusts to the change.

So we might well expect to see an increase in extreme weather events and many are now pointing to recent events as evidence. The problem here is that there have always been extreme events and there have also been previous periods of bunched extreme events. This may be driven by climate cycles, such as the El Nino Southern Oscillation (ENSO). A period that shows many similarities to the last two years is 1974-75 when there was a very strong La Nina event, such as the one we are currently experiencing.

In the timelines above the near back-to-back El Nino events of the 1970s and 2010s are shown in blue (also see them in the chart above the timeline in blue) and various extreme events are shown in red. Much similarity exits, although the severe droughts that have been experienced in the southern US states didn’t show up at all in the 1970s. In fact the Texas drought has been shown as exceptional by any standards.

With so much focus on extreme events and a further focus by many on an apparent plateau seen in global temperatures in recent years, are we perhaps missing some clearer signals buried in the data? One such signal, which got very little media coverage, was published by the WMO at the very end of 2011 and shows last year to be the hottest ever, for a La Nina year (which are typically cooler). In fact every La Nina year over the past 40 years has been warmer than the previous one.

Over six decades and taking just the La Nina years (chart above) there has been a temperature movement of 0.7 deg.C, or 0.12 deg.C per decade. This is somewhat less than the climate sensitivity indicated by the IPCC, but equally it may only be indicative of what is probably the bottom edge of the span of temperature change. It is nevertheless an important trend to understand and follow. Extreme weather events also deserve considerable attention, but there needs to be some increased diligence when it comes to immediately associating them all with climate change.

Later this month the IPCC (Intergovernmental Panel on Climate Change) will launch a very substantial report on Renewable Energy and Climate Change. In advance of that, a “Summary for Policy Makers” was released early this week following the 11^th Session of Working Group III of the IPCC, held in Abu Dhabi on 5-8^th May. In tandem with the Summary document was a press release, which starts out with the words;

Abu Dhabi, 9 May 2011 – Close to 80 percent of the world’s energy supply could be met by renewables by mid-century if backed by the right enabling public policies a new report shows.

Not surprisingly, this key phrase was repeated in headlines the world over, with much media enthusiasm for the report. But it isn’t what the Summary is actually about, nor does the Summary give any details into how this may come about.

Instead, the Summary for Policy Makers provides an extensive overview of the current state of key renewable technologies, including wind, solar, hydro, geothermal, ocean and biomass. There is no doubt, based on the information provided, that renewable energy technologies are maturing rapidly and impressive strides have been made in development and deployment.

The view on the ultimate deployment of renewables and their potential to capture much of the world’s energy market by 2050 comes from a review of some 164 scenarios, with an in-depth review of four. Here it should be noted that the four represent a span from a baseline scenario without a specific mitigation target to three scenarios representing different CO2 stabilization levels. Although we will need to wait for the full report to see the specific details of the scenarios, the fact that they have specific mitigation targets is a telling sign. This implies that these are not scenarios in one important sense, in that they have an artificial constraint which dictates the outcome. Such a constraint doesn’t exist in the real world, but must be developed over time as part of the societal response to energy and climate change issues.

In the current Shell energy scenarios, Blueprints and Scramble, there are no specific mitigation targets at a global level. Rather, the scenarios track different levels of response to the issue of carbon emissions. Blueprints, the more optimistic in terms of a response to climate change, sees the early development of carbon pricing and carbon markets throughout much of the world which in turn drives the rapid deployment of a range of technologies, including renewables, carbon capture and storage and vehicle electrification. It is a bottom-up, national policy driven scenario that pushes technology deployment rates beyond historical norms. By 2100, Blueprints sees stabilization of CO2 at some 540 ppm, with other GHGs adding a further 110 ppm CO2 equivalent. This is above the level that equates to a 2°C rise in global temperatures.

This isn’t to say that targeted scenarios are not instructive. By establishing a future goal and modeling a pathway towards it, we can better understand the role of various technologies and the rates at which they need to be deployed. Such a model also gives insight into the future cost development of certain technologies. The scenario should also test the physical feasibility of the necessary rapid change in the energy system. But none of this means that it is actually possible to achieve such a goal. Society must be suitably motivated to do so and be prepared to shoulder the economic costs, particularly where it involves very early retirement of existing infrastructure.

A key chart in the Summary illustrates the nature of the scenarios that have been sampled.

Category I, II and III scenarios represent CO2 stabilization levels below 485 ppm, a level at which many observers regrettably now see as unobtainable. The green Category I scenarios see stabilization at current levels or below, which implies the deployment of air capture technologies or very large scale use of bio-char sequestration or similar.

Although there isn’t sufficient information in the Summary to extract the underlying numbers, the chart above also implies that the 2050 world in many of the scenarios uses less energy (or at least not that much more) than the current world (492 EJ in 2008). This is due in part to the calculation method for primary energy differing between fossil energy and renewable energy, but it would also appear that tremendous improvements in energy efficiency are made. This was a key feature of the “100% renewable energy by 2050” scenario that WWF released recently. The real story in that scenario was not the renewables per se (where total deployment was not that different to the Shell Blueprints scenario), but the transformation in energy use that accompanied them. This almost certainly requires yet another step change in societal response – it is unlikely to be just about better technology.

As we head towards the IPCC 5^th Assessment Report this contribution from Working Group III is likely to be an important milestone and much referred to in the coming months. But we should recognize it for what it appears to be and not be. It certainly appears to be a very thorough review of the current state of renewable energy technologies and an important guide as to how they may contribute to the energy system of the future. But this isn’t  a forecast of what will be, nor does it appear to be a clear guide as to what is actually doable in the limited time available to respond, particularly given the current economic circumstances the world is experiencing and the political stalemate over carbon emissions that we see in some major economies.