The Physical Science Basis for climate change, which was released in August 2021 as a key element of the forthcoming sixth global assessment from the UN’s Intergovernmental Panel on Climate Change (IPCC), is setting the tone for discussions and commitments from across the international community towards a future net zero world, writes Jonathan Spencer Jones.
As you read this the latest annual Conference of the Parties (COP) to the UN Framework Convention on Climate Change (UNFCCC) event, COP26, will be under way in Glasgow, Scotland or will already have taken place.
In the early days – the first assessment from the UN’s Intergovernmental Panel on Climate Change (IPCC) was published as far back as 1990 and COP1 was in 1995 – the subject was mainly the preserve of academics and researchers in the field and governments. Over time, both the successive publications and events have become progressively larger, more diverse and more widely publicised.
Notable milestones have been the COP3 Kyoto Protocol of 1997 and more recently the Paris Agreement of COP21 in 2015, which represents the most recent widely agreed statement on climate and emissions targets. Under the Paris Agreement, the increase in global average temperature is intended to be well below 2°C above pre-industrial levels and preferably limited to 1.5°C, while peaking of greenhouse gas emissions is met as soon as possible towards net zero in the second half of this century.
Since then the mantra of ‘Net zero by 2050’ has emerged, which has been taken up by bodies such as the International Energy Agency (IEA) and organisations and companies that have put out plans to meet this target.
So far (as of mid-September), however, only one government has officially mandated the target – the UK, and host to COP26. As part of that commitment the UK also has put in place aggressive targets for 2030 including a 68% reduction in greenhouse gas levels compared to 1990 and actions including a ban on sales of new cars and vans from that year.
As the host to COP26, unsurprisingly a goal of the event from the UK perspective is to secure similarly ambitious 2030 targets from other countries. Other goals are the by now standard commitments to raising financing – at least $100 billion per year agreed by developed countries – and to working together to protect communities and habitats impacted by climate change and to deliver on the Paris Agreement.
Specific delivery directions highlighted for 2030 include accelerating the phase-out of coal, speeding up the switch to electric vehicles and encouraging investment in renewables as well as curtailing deforestation.
How many countries will commit to a net zero by 2050 goal remains to be seen and many eyes will be on the UK in the months and years ahead. While the politicians driving the agenda are understandably gung-ho and there is wide support, there also is growing public concern with the realisation of the costs involved and the impacts on incomes and lifestyles that aren’t always made clear.
So far, much of the delivery of the climate agenda has been at a high level. But as targets become more stringent and decarbonisation deepens across the economy, the consumer impacts will become increasingly apparent. Their support is essential for a successful transition.
The Physical Science basis
The almost 4,000 page Physical Science Basis report is without doubt the most comprehensive so far, involving the input of over 200 authors and based on 14,000 publications.
The authors claim both much better understanding of climate change now than when the IPCC started and continual improvements in climate modelling, measured by comparing simulations against historical observations. (Note the notoriously unreliable weather forecasting is a subset of these, with weather pertaining to short term conditions and climate the longer term over time.)
What then are some of the highlights?
1.5°C in jeopardy
The global average surface temperature increase above the pre-1900 level is projected to reach 1.5°C by 2040 in all the scenarios considered – ranging from the most optimistic emissions declining below net zero to a fossil fuel rich, high emission world.
In the best case there could be a subsequent overshoot followed by a slight decline to 1.4°C by 2100, while the other scenarios have the temperature approaching or exceeding 2°C by then.
Humans are to blame
The main human drivers of climate change are increases in the atmospheric concentrations of greenhouse gases and of aerosols from burning fossil fuels, land use and other sources. The current rates of increase of the concentration of these, in particular CO2, methane and nitrous oxide, are “unprecedented over at least the last 800,000 years”.
Evidence from tree rings and other records shows the rate of global surface temperature increase over the past fifty years has exceeded that of any 50-year period over the past 2,000 years.
The climate is to blame
Based on the science of ‘event attribution’, human-caused global warming has resulted in changes in a wide variety of recent extreme weather events including heatwaves, heavy rainfall, drought, tropical cyclones and associated wildfires and coastal flooding.
With a warmer temperature, the atmosphere can hold more water and there is more and faster evaporation, and resultant heavier precipitation.
As the planet warms, climate change does not unfold uniformly across the globe, but some patterns of regional change show “clear, direct and consistent relationships to increases in global surface temperature”.
The Arctic warms more than other regions, land areas warm more than the ocean surface and the northern hemisphere more than the southern hemisphere. Precipitation increases over the high latitudes, tropics and large parts of the monsoon regions, but decreases over the subtropics.
Warnings from the past
In the past, the Earth has experienced prolonged periods of elevated greenhouse gas concentrations that caused global temperatures and sea levels to rise.
In an example roughly 125,000 years ago, slight variations in the Earth’s orbit triggered an increase of about 1-2°C of global warming and 2–8m of sea level rise relative to the 1900 level, even though atmospheric CO2 concentrations were similar to 1900 values.
Climate sinks are weakening
About half of the CO2 that human activities have emitted to the atmosphere has been taken up by natural sinks such as forests, soils and oceans. However, there are signs that these processes are being impacted by the increasing CO2 in the atmosphere and climate change in a way that will weaken their take-up capacity in the future.
Methane to the fore
Methane (CH4), which is a much more powerful greenhouse gas than CO2 but more short lived, has become of greater concern, having increased at a growing rate over the past decade – about 3.5% higher in 2019 than in 2011. This growth is attributed primarily to fossil fuels and agriculture dominated by livestock as well as landfills.
Proposals to remove CH4 from the atmosphere, both directly and microbially, are emerging, although the topic is still in its infancy.
Over the next twenty years emissions of greenhouse gases are expected to continue, further increasing concentrations of greenhouse gases in the atmosphere and leading to continued trends including shrinking of the ice sheets in the Arctic and Antarctic and thermal expansion of the oceans.
However, there are uncertainties due to natural events such as volcanic eruptions, which can impact on scales from the local
Some reversibility is possible
Deliberate removal of CO2 from the atmosphere could reverse some aspects of climate change – but only if there is a net reduction, i.e. the removals are larger than emissions.
Some trends, such as the increase in global surface temperature, would start to reverse within a few years. Others such as permafrost thawing would take decades to reverse, while others still such as acidification of the deep ocean would take centuries and sea level rise centuries to millennia.
Last but not least, ‘tipping points’ or thresholds in the climate system that could lead to a disproportionate response such as strongly increased Antarctic ice sheet melting, permafrost thawing or forest dieback, cannot be ruled out.
Insights from the industry
Cletus Bertin, Executive Director, CARILEC: “We note that countries are being asked to come forward with ambitious 2030 emissions reductions targets. While we are mindful that the setting of aspirational and ambitious goals can be inspirational, we would also like to see the setting of realistic, i.e. evidenced-based, and feasible targets for the reduction of final energy consumption and the percentage share of renewable energy.
“Developing countries, in particular, should be encouraged to urgently establish and operationalise the required policy, legislative and regulatory frameworks, and mechanisms in this regard.”
Reji Kumar Pillai, President India Smart Grid Forum and Chairman, Global Smart Energy Federation: “All countries are talking about increasing the targets of renewable energy, but very few have set a target for retiring coal power plants. COP26 should mandate all countries to set a firm roadmap for retiring coal plants.
“The biggest problem facing humanity is the constantly increasing atmospheric temperature. In India summer temperatures are already above 48oC and may exceed 50oC before the end of this decade, making living, working and commuting impossible. Less than 10% of the households own room air conditioners and similarly in most developing countries.”
Julia Hamm, President and CEO, Smart Electric Power Alliance: “Now is the time for aggressive action to combat climate change. As SEPA identified through our Utility Transformation Challenge surveys, electric utilities are making progress towards carbon reduction, but much work remains. Bold commitments from COP26 are a key catalyst for an accelerated energy transition.