Increases in greenhouse gases result in a change in the Earth’s energy budget in the infrared – at a rate of 0.04 Watts/per metre squared/per year. Annual background variability is some 100 times that. Natural variability in the Earth energy budget is driven by clouds, ice, vegetation, atmospheric moisture and sea surface temperature. Especially clouds over decades it seems.
The chart below shows changes in infrared out in the tropics measured by different instruments from 1978. The (a) plot shows the results with no overlap correction and (b) with overlap correction. The variability is largely a result of air temperature, cloud cover and height and atmospheric moisture variability associated with the La Niña/El Niño system in the tropical Pacific.
Source: Loeb et al 2012
In recent decades surface temperature reflects tropical cloud cover. In particular – the warming to 1998, the step change to increased cloud aroun d the turn of the century and little change since.
Surface temperature more generally has regime changes – warming to 1946, cooling to 1976, warming to 1998 and little change since. These in turn follow states of ocean circulation in the Pacific. Not just correlation but a precise correspondence.
Source: Hadley Centre
Much of the variability in surface temperature is quite natural. The warmer and cooler regimes are marked by changes in the frequency and intensity of El Niño and La Niña and of changes in the northeast Pacific known as the Pacific Decadal Oscillation. El Niño dominant from 1912, La Niña to 1946, El Niño again to 1998 and La Niña – marginally – since. With abrupt shifts between states driven by internal variability in the climate system. The rate of increase in temperature between 1946 and 1998 – a complete warming and cooling regime – was 0.07 degrees centigrade per decade. Assuming all late century warming was anthropogenic makes it an upper bound on the rate of slow temperature increase – but reveals nothing about natural variability.
Unlike El Niño and La Niña, which may occur every 3 to 7 years and last from 6 to 18 months, the PDO can remain in the same phase for 20 to 30 years. The shift in the PDO can have significant implications for global climate, affecting Pacific and Atlantic hurricane activity, droughts and flooding around the Pacific basin, the productivity of marine ecosystems, and global land temperature patterns. This multi-year Pacific Decadal Oscillation ‘cool’ trend can intensify La Niña or diminish El Niño impacts around the Pacific basin,” said Bill Patzert, an oceanographer and climatologist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “The persistence of this large-scale pattern [in 2008] tells us there is much more than an isolated La Niña occurring in the Pacific Ocean.”
Natural, large-scale climate patterns like the PDO and El Niño-La Niña are superimposed on global warming caused by increasing concentrations of greenhouse gases and landscape changes like deforestation. According to Josh Willis, JPL oceanographer and climate scientist, “These natural climate phenomena can sometimes hide global warming caused by human activities. Or they can have the opposite effect of accentuating it.” </blockquote>NASA Earth Observatory
The graph below shows a millennia long record of El Niño and La Niña – more salt in the Law Dome ice core is La Niña – showing a 20th century high point in El Niño activity and hundreds of years of La Niña dominance before that. A solar driver for this variability seems likely. The question is – can this have longer term impacts on temperature than just the 20 to 30 years cooling and warming periods discussed by NASA? How much of 20th century warming was the result of the 20th century peak in El Niño? Was there a peak in El Niño or will it go higher? What are the implications of a return to La Niña over hundreds of years?
Source: Vance et al 2013
There is some suggestion that solar activity peaked in the 20th century after hundreds of years of low activity with effects amplified through terrestrial systems.
And a link to global surface temperature.
Source: PAGES 2K Consortium 2013
But… but… but… models?
The abrupt changes of the past are not fully explained yet, and climate models typically underestimate the size, speed, and extent of those changes. Hence, future abrupt changes cannot be predicted with confidence, and climate surprises are to be expected.
The new paradigm of an abruptly changing climatic system has been well established by research over the last decade, but this new thinking is little known and scarcely appreciated in the wider community of natural and social scientists and policy-makers. At present, there is no plan for improving our understanding of the issue, no research priorities have been identified, and no policy-making body is addressing the many concerns raised by the potential for abrupt climate change. Given these gaps, the US Global Change Research Program asked the National Research Council to establish the Committee on Abrupt Climate Change and charged the group to describe the current state of knowledge in the field and recommend ways to fill in the knowledge gaps.
It is important not to be fatalistic about the threats posed by abrupt climate change. Societies have faced both gradual and abrupt climate changes for millennia and have learned to adapt through various mechanisms, such as moving indoors, developing irrigation for crops, and migrating away from inhospitable regions. Nevertheless, because climate change will likely continue in the coming decades, denying the likelihood or downplaying the relevance of past abrupt events could be costly. Societies can take steps to face the potential for abrupt climate change. The committee believes that increased knowledge is the best way to improve the effectiveness of response, and thus that research into the causes, patterns, and likelihood of abrupt climate change can help reduce vulnerabilities and increase our adaptive capabilities…
What defines a climate change as abrupt? Technically, an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause. Chaotic processes in the climate system may allow the cause of such an abrupt climate change to be undetectably small. </blockquote> NAS 2002
Unfortunately – coming to an understanding of variability in a chaotic climate system is far easier said than done. The proper response to uncertainty is build resilience in communities and ecologies. Unfortunately again – there is very little uncertainly to be found in the simple ideas of advocates and the simple minded ‘solutions’ of true believers. Building resilience is based on both on restoring agricultural soils and ecologies as well as securing and growing economies.
The Intergovernmental Panel on Climate Change (IPCC) estimated that carbon loss from agriculture and forestry contributed 660 billion tons (165 parts per million) of carbon dioxide to the atmosphere. Much of this can be returned to soils and vegetation using regenerative farming and ecological restoration at a cost of about US$0.5 trillion – some of which may come from aid for ‘smart development goals’.
Carbon sequestration in soils has major benefits in addition to offsetting anthropogenic emissions – from fossil fuel combustion, land use conversion, soil cultivation, continuous grazing and cement manufacturing. Restoring soil carbon stores increases agronomic productivity and enhances global food security. Increasing the soil organic content enhances water holding capacity and creates a more drought tolerant agriculture – with less downstream flooding. There is a critical level of soil carbon that is essential to maximising the effectiveness of water and nutrient inputs. Global food security, especially for countries with fragile soils and harsh climate such as in sub-Saharan Africa and South Asia, cannot be achieved without improving soil quality through an increase in soil organic content. Wildlife flourishes on restored lands helping to halt biodiversity loss. Reversing soil carbon loss is a new green revolution where conventional agriculture is hitting a productivity barrier with exhausted soils and increasingly expensive inputs.
Increased agricultural productivity, increased downstream processing and access to markets build local economies and global wealth. Economic growth provides resources for solving problems – conserving and restoring ecosystems, better sanitation and safer water, better health and education, updating the diesel fleet and other productive assets to emit less black carbon, developing better and cheaper ways of producing electricity, replacing cooking with wood and dung with better ways of preparing food thus avoiding respiratory disease and again reducing black carbon emissions. The warming potential of black carbon is equal to that of carbon dioxide emission from electricity production – but is given little attention in the public sphere. A global program of agricultural soils restoration is the foundation for balancing the human ecology. In this international year of soils – France has committed to increasing soil carbon by 0.4% per year. As a global objective and given the highest priority it is a solution to critical problems of biodiversity loss, development, food security and resilience to drought and flood.
The contrast with commitments on energy is stark. The International Energy Agency added the commitments made and it totals to a 3.7 billion increase in emissions to 2030 at a cost of US$13.5 trillion for wind and solar subsidies. An energy transition seems inevitable as technologies emerge and fossil fuel costs increase. But there little benefit to be gained from implementing ineffective energy technology for the sake of ideology.