Climate Change
Conventional wisdom about global warming is accepted by the Supreme Court but the facts suggest there’s no need to panic, writes Nick Mulcahy
Conventional wisdom about global warming extends to the Supreme Court. Evidence of its impact suggests panic is unwarranted
Two different perspectives on climate change were provided recently, one in Ireland’s Supreme Court and the other by an expert on the subject, Ole Humlum, and Emeritus Professor of Physical Geography at the University of Oslo.
In the seven-judge Supreme Court, there was no dissension from chief justice Frank Clarke’s ruling in a case where Friends of the Irish Environment succeeded in striking down the government’s 2017 National Mitigation Plan for lack of specificity.
Among other things, chief justice Clarke declared:
● Climate change is undoubtedly one of the greatest challenges facing all states. Ireland is no different.
● The broad underlying scientific evidence as to the causes of and problems created by climate change are not in dispute.
● The climate system shows a delayed response to the emissions of greenhouse gases, meaning that the full warming effect of gases which are emitted today will only become apparent some 30 to 40 years in the future.
● Studies have indicated that there is a consistent and almost linear relationship between carbon dioxide emissions and projected global temperature increases over the next 80 years.
● Climate change is already having a profound environmental and societal impact in Ireland and is predicted to pose further risks to the environment, both in Ireland and globally, in the future.
● Future impacts of climate change are predicted to include further increases in global temperatures, rising sea levels and an increase in extreme weather events, such as episodes of flooding and drought.
● There are also reported increased risks of mortality and morbidity, as climate-related extremes may place food systems at risk, lead to water shortages and the emergence of new pests and diseases, while also contributing to significant changes in the ecosystems of many plants and animals.
● The more global warming proceeds to a level which is 2°C higher than typical temperatures at the beginning of the Industrial Revolution, the greater are such risks.
● There is a general consensus in climate science that, if the effects of global warming are to be mitigated or reduced, the rise in global temperatures should not exceed 2°C above pre-industrial levels.
● It can safely be said that the consequences of failing to address climate change are accepted as being very severe with potential significant risk both to life and health throughout the world but also including Ireland.
● There are strong suggestions that even a level of global warming limited to below 2°C may give rise to some important tipping elements.
● While it is not possible to predict the precise temperatures at which irreversible adverse events will occur, there does appear to be a consensus that the risk of such tipping points occurring is materially increased as temperatures themselves rise.
● The evidence that the practical irreversibility and significant consequences of reaching some of the tipping points in question adds a further imperative to the early tackling of global warming.
Justice Clarke’s observations sum up nicely the conventional wisdom surrounding climate change, and among politicians there is little or no dispute about the perils that lie ahead if carbon emissions in Ireland are not reduced. Reducing carbon emissions in Ireland won’t put a cap on total global emissions, but what matters – not just in Ireland but across the EU – is doing the right thing, no matter the consequences to the domestic economy.
The Supreme Court ‘quashed’ Ireland’s National Mitigation Plan on the basis that it wasn’t specific enough about emission reduction measures out to 2050. Anticipating the ruling, the Department of Climate Action has been preparing a new Climate Action Bill, which minister Eamon Ryan has promised to unveil sometime in October. This new law and plan will specify in detail how Ireland is to achieve a net-zero economy by 2050 — the ‘national transition objective’.
So time is definitely running out for climate change sceptics to stand up and make their point. For instance, government has already signaled that Ryan’s new Climate Action Bill will ban the sale of new fossil-fuel cars from 2030 and stop the grant of NCT certificates from 2045. This will enshrine in law previous commitments made under the 2019 Climate Action Plan.
Though at this point there’s no gainsaying such drastic measures, speculation around tipping points is just that, and actual evidence of climate change impacts is far less alarmist than Justice Clarke assumes. Over to Prof. Humlum’s report, The State of the Climate 2019, some of which is extracted below.
● Air Temperatures Considering the entire surface air temperature record since 1850 or 1880, 2019 was a very warm year, but in all global temperature records it was cooler than 2016. However, the decrease in temperatures characterising 2017 and 2018 was interrupted by a renewed, moderate El Niño episode, underlining the importance of ocean–atmosphere exchanges.
Satellite data since 1979 reveal that lower troposphere temperatures have increased over both land and oceans, but most clearly over land. The most uncomplicated explanation for this is that much of the warming is caused by solar insolation, but there may well be several supplementary reasons such as changes in cloud cover and land use.
● Ocean Temperatures Since 2004, the upper 1,900 m of the oceans have experienced net warming. The maximum warming (0.08–0.23°C) affects the uppermost 200 m of the oceans, and mainly in regions near the Equator, where the greatest amount of solar radiation is received. At greater depths, a small (about 0.02°C) net warming occurred between 2004 and 2019.
Simultaneously, the northern oceans have, on average, experienced a marked cooling down to 1,400 m, and slight warming at greater depths. The southern oceans have seen slight warming at most depths, but most clearly near the surface.
● In 2019, the global seaice extent remained well below the average for the satellite era (since 1979), but exhibited stability or a
Sea Ice
slightly rising trend through 2019. At the end of 2016, the global sea-ice extent reached a marked minimum. The minima have now passed, and a trend towards stable or higher ice extent at both poles may have begun during 2019.
● Variations in global snow cover are mainly caused by changes in the Northern Hemisphere. Southern Hemisphere snow cover is essentially controlled by the Antarctic ice sheet, and is therefore relatively stable. Northern Hemisphere average snow-cover extent has also been stable since the onset of satellite observations, although local and regional inter-annual variations may be large.
Considering seasonal changes since 1979, the Northern Hemisphere snow cover autumn extent is slightly increasing, the mid-winter extent is largely stable, and the spring extent has been slightly decreasing. In 2019, the Northern Hemisphere seasonal snowcover extent was close to that of the preceding years.
Snow Cover
● While the satellitederived record suggests a global sea-level rise of about 3.2mm per year or more, data from tide gauges along coasts all over the world suggest a stable, average global sea-level rise of less than 1.5mm per year (there are 1,000mm in 1 metre). The noticeable difference (at least 1:2) between the satellite and tide gauge datasets has no broadly accepted explanation. Neither of the two types of measurements indicate any modern acceleration in sea-level rise.
Sea Level Storms and Hurricanes
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The most recent data on global tropical storm and hurricane accumulated cyclone energy (ACE) is well within the range experienced since 1970. The ACE data series displays considerable variability but without any clear trend towards higher or lower values. A longer series for the Atlantic Basin (since 1850) suggests a natural cycle of about 60 years’ duration in tropical storm and hurricane ACE. In addition, modern data on hurricanes land-falling in the continental USA suggests these remain within the normal range.