Good news about climate change!

Larry Kummer, Editor

13 years ago

Summary: To start your week on a pleasant note, here are articles giving good news from climate scientists. It’s easily lost amidst the predictions of apocalypse soon. At the very least, these suggest that we have more time to prepare than commonly expected.

Contents

Update on the rising seas
New research about the effect of more CO2
The big picture about climate change
For More Information

(1) Update on the rising seas

Many experts have disputed claims that rising sea levels were affecting Pacific islands, attributing the damage to their inhabitants wrecking their ecosystems. Slowly the news media takes notice: “Shape-shifting islands defy sea-level rise “, New Scientist, 10 June 2010 (gated) — The full article is gated. For more details see “Pacific islands growing, not sinking“, ABC News. Opening:

For years, people have warned that the smallest nations on the planet – island states that barely rise out of the ocean – face being wiped off the map by rising sea levels. Now the first analysis of the data broadly suggests the opposite: most have remained stable over the last 60 years, while some have even grown.

Even better news comes from new research that shows the oceans continue to rise at the same rates as during the past several centuries, although forecast to accelerate. See “Seas will rise no more than 69 centimetres by 2100“, New Scientist, 14 May 2013

A comprehensive study of the behaviour of ice sheets suggests that … sea levels will rise by 16 to 69 cm {7″ – 27″} by 2100. That’s not too far off the best estimate in the last report of the Intergovernmental Panel on Climate Change (IPCC) in 2007: it predicted 18 to 59 cm {7″ – 23″} by 2100.

See the actual research for details:

Observations of Sea Level Changes, Fourth Assessment Report, IPCC, 2007 — Forecasts a rise of 18 to 59 cm {7″ – 23″} by 2100.
The Budget of Recent Global Sea Level Rise 2005–2012, NOAA, June 2012
“Is There a 60-Year Oscillation in Global Mean Sea Level?“, Don P. Chambers, Mark A. Merrifield, and R. Steven Nerem, Geophysical Research Letters, 16 September 2012
“Continental mass change from GRACE over 2002–2011 and its impact on sea level“, Baur, Kuhn, and Featherstone, Journal of Geology, February 2013

(2) Important new research about the sensitivity of global temperature to rising CO2 levels

One of the active fronts in climate science is research to determine the effect of rising CO2 on global temperatures, with several high-profile papers published this year.

(a) The news media reports the debate (updated)

“Climate slowdown means extreme rates of warming ‘not as likely’“, BBC, 19 May 2013 — Excerpt:

Since 1998, there has been an unexplained “standstill” in the heating of the Earth’s atmosphere. Writing in Nature Geoscience, the researchers say this will reduce predicted warming in the coming decades. But long-term, the expected temperature rises will not alter significantly.

“A second chance to save the climate“, New Scientist, 19 May 2013 — Opening:

“Humanity has a second chance to stop dangerous climate change. Temperature data from the last decade offers an unexpected opportunity to stay below the agreed international target of 2 °C of global warming. A new analysis took temperature rise in the most recent decades, and worked out what this means for the coming ones. It suggests that Earth will warm more slowly over this century than we thought it would, buying us a little more time to cut our greenhouse gas emissions and prevent dangerous climate change.”

“Study opens new cracks in scientific front on climate change“, Gerard Wynn (columnist), Reuters, 21 June 2013 — Opening:

A major recent study has put the cat among the pigeons on climate change, challenging the size of the problem in the near-term and the role of a recent slowdown in warming. The paper, published in the journal Nature Geoscience in May, involved scientists from 14 institutions and calculated that more extreme climate change was now less likely, after taking into account slower warming in the past decade.

The notion of changing a view as a result of a single decade of observations is somewhat controversial, given that natural patterns can span several decades. And the paper applied a method for estimating future climate change which is known to produce lower warming estimates than a corresponding measure used by the U.N. climate panel, the Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA).

“A peek inside the next IPCC assessment“, The Economist, 20 July 2013 — Opening:

“THAT report is going to scare the wits out of everyone,” said Yvo de Boer recently. He is a former United Nations chief climate negotiator and was talking about the forthcoming fifth assessment by the Intergovernmental Panel on Climate Change (IPCC). With two months to go before the assessment is to be published, however, one sign suggests it might be less terrifying than it could have been.

The sign in question is about climate sensitivity. This is the measure used by researchers of how much they expect the world’s average temperature to increase in response to particular increases in levels of carbon dioxide in the atmosphere. According to one table from the unpublished report, which was seen by The Economist (above), at CO₂ concentrations of between 425 parts per million and 485 ppm, temperatures in 2100 would be 1.3-1.7°C above their pre-industrial levels. That seems lower than the IPCC’s previous assessment, made in 2007. Then, it thought concentrations of 445-490 ppm were likely to result in a rise in temperature of 2.0-2.4°C.

(b) A climate scientist discusses the new research

For more detailed coverage of the debate, I recommend reading these articles by Judith Curry (an eminent climate scientist) at her website, Climate Etc. They describe the major new papers, put them in a larger context, and describe the trend of the debate.

New perspectives on climate sensitivity, 19 March 2013 — “Here is a summary of some important new papers on the topics of climate sensitivity and attribution.”
Mainstreaming ECS ~ 2 C, 19 May 2013 — “IPCC lead authors are paying attention to the lower sensitivity estimates. It will be very interesting to see how the IPCC AR5 plays this … {and} if the IPCC budges from the 2-4.5 C range that has remained unchanged since the 1979 Charney report.”

“Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models“, Piers M. Forster et al, Journal of Geophysical Research – Atmospheres, 6 February 2013

“The upper end of climate model temperature projections is inconsistent with past warming“, Peter Stott et al, Environmental Research Letters, 19 February 2013 — Abstract:

Climate models predict a large range of possible future temperatures for a particular scenario of future emissions of greenhouse gases and other anthropogenic forcings of climate. Given that further warming in coming decades could threaten increasing risks of climatic disruption, it is important to determine whether model projections are consistent with temperature changes already observed. This can be achieved by quantifying the extent to which increases in well mixed greenhouse gases and changes in other anthropogenic and natural forcings have already altered temperature patterns around the globe.

Here, for the first time, we combine multiple climate models into a single synthesized estimate of future warming rates consistent with past temperature changes. We show that the observed evolution of near-surface temperatures appears to indicate lower ranges (5–95%) for warming (0.35–0.82 K and 0.45–0.93 K by the 2020s (2020–9) relative to 1986–2005 under the RCP4.5 and 8.5 scenarios respectively) than the equivalent ranges projected by the CMIP5 climate models (0.48–1.00 K and 0.51–1.16 K respectively). Our results indicate that for each RCP the upper end of the range of CMIP5 climate model projections is inconsistent with past warming.

“Energy budget constraints on climate response“, Alexander Otto et al, Nature Geoscience, 19 May 2013

The most likely value of equilibrium climate sensitivity {ECS} based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2– 3.9 °C , compared with the 1970–2009 estimate of 1.9 °C (0.9–5.0 °C). Including the period from 2000 to 2009 into the 40-year 1970–2009 period delivers a finite upper boundary, in contrast with earlier estimates calculated using the same method. The range derived from the 2000s overlaps with estimates from earlier decades and with the range of ECS values from current climate models (ECS values in the CMIP5 ensemble are 2.2–4.7 °C), although it is moved slightly towards lower values. Observations of the energy budget alone do not rule out an ECS value below 2 °C, but they do rule out an ECS below 1.2 °C with 95% confidence.

… The best estimate of TCR based on observations of the most recent decade is 1.3 °C (0.9–2.0 °C). This is lower than estimates derived from data of the 1990s (1.6 °C (0.9–3.1 °C) or for the 1970–2009 period as a whole (1.4 °C (0.7–2.5 °C)). Our results match those of other observation-based studies and suggest that the TCRs of some of the models in the CMIP5 ensemble with the strongest climate response to increases in atmospheric CO2 levels may be inconsistent with recent observations — even though their ECS values are consistent and they agree well with the observed climatology. Most of the climate models of the CMIP5 ensemble are, however, consistent with the observations used here in terms of both ECS and TCR.

“An objective Bayesian, improved approach for applying optimal fingerprint techniques to estimate climate sensitivity“, Nicholas Lewis, Journal of Climate, in press

Incorporating six years of unused model-simulation data and revising the experimental design to improve diagnostic power reduces the best-fit climate sensitivity. Employing the improved methodology, preferred 90% bounds of 1.2–2.2 K for ECS are then derived (mode and median 1.6 K). The mode is identical to those from Aldrin et al. (2012) and (using the same, HadCRUT4, observational dataset) Ring et al. (2012). Incorporating forcing and observational surface temperature uncertainties, unlike in the original study, widens the 90% range to 1.0–3.0 K.

Update: “Has the magnitude of floods across the USA changed with global CO2 levels?“, RM Hirsch and KR Ryberg (both with USGS), Hydrological Sciences Journal, Issue 1, 2012 — Abstract:

Statistical relationships between annual floods at 200 long-term (85–127 years of record) streamgauges in the coterminous United States and the global mean carbon dioxide concentration (GMCO2) record are explored. The streamgauge locations are limited to those with little or no regulation or urban development. The coterminous US is divided into 4 large regions and stationary bootstrapping is used to evaluate if the patterns of these statistical associations are significantly different from what would be expected under the null hypothesis that flood magnitudes are independent of GMCO2.

In none of the four regions defined in this study is there strong statistical evidence for flood magnitudes increasing with increasing GMCO2. One region, the southwest, showed a statistically significant negative relationship between GMCO2 and flood magnitudes. The statistical methods applied compensate both for the inter-site correlation of flood magnitudes and the shorter-term (up to a few decades) serial correlation of floods.

(3) The big picture about climate change

While cheering madly for their faction of scientists, laypeople often lose sight of the big picture — the key elements for making public policy about this important issue.

The major global temperature measurement systems tell — broadly speaking — the same story since the late 1970s: two decades of warming, followed by a pause.
This is consistent with the larger firm conclusions of climate scientists: two centuries of warming, coming in pulses (ie, waves), with anthropogenic factors becoming the largest (not the only) drivers since roughly 1950.
The work of the IPCC and the major science institutes are the best guides for information about these issues.
There is a debate about the attribution (causes) of past warming — which probably varied over time — between natural drivers (eg, rebound from the Little Ice Age, solar influences) and anthropogenic drivers (eg, CO2, aerosols, land use changes). The IPCC reports make few claims about attribution of current climate activity to warming to date, as that remains actively debated in the literature.
There is an even larger debate about climate forecasts, both the extent of future CO2 emissions, and the net effects of the various natural and anthropogenic drivers.

For the past five years my recommendations have been the same:

More funding for climate sciences. Many key aspects (eg, global temperature data collection and analysis) are grossly underfunded.
Wider involvement of relevant experts in this debate. For example, geologists, statisticians and software engineers have been largely excluded — although their fields of knowledge are deeply involved.