In the Spring of 2012, the Netherlands Environmental Assessment Agency PBL held a survey among 1868 scientists studying various aspects of climate change, including physical climate, climate impacts, and mitigation. The main results of the survey were published in an article in Environmental Science and Technology (ES&T) in August 2014: “Scientists’ views about attribution of global warming”. It showed that there is widespread agreement regarding a dominant influence of anthropogenic greenhouse gases on recent global warming. This agreement is stronger among respondents with more peer-reviewed publications.
A background report with the results for all 31 questions has now been made available. The total number of responses for each answer option is provided and a subdivision into seven groups for five questions. The background report contains previously unpublished data. Some highlights are provided below.
Respondents were asked for their opinion regarding the best estimate and likely range for equilibrium climate sensitivity (ECS). This is an important quantity for projections of global warming, as it gives the expected warming that would follow from a doubling in atmospheric CO2 concentration after the climate system has equilibrated to the new conditions. Thus, expected warming in the future depends on the combination of total emissions and climate sensitivity.
The figure below gives the average estimates of ECS from 7 groups of respondents, including authors of the Working Group I report of the fourth IPCC Assesment Report (AR4), respondents who signed public declarations critical of mainstream climate science as embodied by IPCC (‘unconvinced’), and four different subgroups distinguished according to their self-declared number of climate related peer-reviewed publications (0–3; 4–10; 11–30; more than 30). Results from most groups were very close to the IPCC range (1.5-4.5 °C) mentioned in the fifth assessment report (AR5) – except those tagged as ‘unconvinced’ which strongly deviated from the other groups, and to a lesser extent the group of respondents with three or less publications. For all subgroups the ‘best estimate’ was slightly lower than the ‘best estimate’ reported in AR4 (i.e. 3 °C). AR5 provided no best estimate.
Role of climate science in society
Respondents were also asked their opinion about seven statements regarding the role of climate science in society and how the science should be communicated. There was a strong consensus that scientists themselves should communicate with both policymakers and the general public about climate change and that communication with the general public should focus on solid knowledge. To a lesser extent there was agreement that risks and uncertainties should be emphasised during such communication. Responses varied more strongly about whether or not existing uncertainties in climate science strengthen the case for mitigation (i.e. to avoid potential low probability, high impact events). There was (strong) disagreement with the statement that climate science would be too uncertain to be useful for policymaking on climate change.
The role of the sun in global warming
In the public debate about climate change the role of the sun is often put forward as an alternative explanation for global warming. Question 17 asked what fraction of recent global warming could be attributed to the sun. Those tagged as ‘unconvinced’ had the lowest fraction of respondents that indicated that they don’t know (together with AR4 authors) and the highest fraction that said that the role of the sun is unknown. As expected they also had by far the highest fraction (27%) that believed that the sun caused more than half of recent global warming.
As with the attribution questions (see the ES&T article), there appears to be a trend in responses going from the group with fewest publications to those with most. The more publications about climate change respondents report to have written, the larger fraction of them agree with the IPCC position that the sun hardly played a role in recent global warming, since the solar output decreased slightly over that period.
- To the background report
- ES&T article (Open Access)
- Comment on Scientists’ Views about Attribution of Global Warming
- Reply to Comment on Scientists’ Views about Attribution of Global Warming
- Blogpost with the ES&T article
- Video-interview with Collin Maessen about the ES&T article
- FAQ’s with the ES&T article
PS: I’ll have a poster presentation about the survey at the EGU conference this week, in session EOS6 “Communication and Education in Geoscience” on Thursday evening.