The term ‘Little Ice Age’ refers to a period of cooler temperatures between around 1400 and 1850, although a range of dates are used. This climate feature has been inferred from various types of direct and indirect evidence, but it is still not clear how widespread these cooler temperatures were.
A new article by Lockwood et al explores some of the commonly used indirect evidence such as paintings and the occurrence of ‘frost fairs’ on the Thames. We also address the common assumption that the cooler temperatures were solely due to a reduction in solar activity (the Spörer and Maunder minima). Although this assumption is almost certainly wrong, the two features are sometimes considered to be synonymous.
The Committee on Science, Space & Technology of the US House of Representatives conducts regular evidence hearings on various science topics. On Wednesday 29th March, there is a hearing on “Climate science: assumptions, policy implications, and the scientific method”. The following letter, summarising the scientific findings of Fyfe et al. (2016) and Karl et al. (2015), has been submitted as evidence to this hearing.
The broader context is that the Committee Chairman, Mr. Lamar Smith, has previously discussed the findings of Fyfe et al. (of which I was a co-author), claiming: “A new peer-reviewed study, published in the journal Nature, confirms the halt in global warming”. This statement is incorrect, and motivated the clarification on what Fyfe et al. actually says.
Scientists can’t do everything by themselves. We need to engage the millions of citizens who are passionate about knowledge to help solve scientific mysteries and improve our understanding of the world around us.
Those with more technical knowledge might also contribute by communicating climate change in novel ways. Recently, Kevin Pluck (a software engineer) created a global sea ice spiral which gained widespread attention on social media – here he tells Climate Lab Book how he did it. Continue reading Animating global sea ice changes→
The UN Paris Agreement on climate change aims to ensure increases in global temperature are less than 2°C above ‘pre-industrial’ levels, with an aspirational 1.5°C limit. However, the ‘starting line’ of the pre-industrial era is not defined by the UN agreements, or by the Intergovernmental Panel on Climate Change (IPCC).
A new analysis by an international team of researchers aims to better define the pre-industrial baseline, informing the world’s decision makers on the required limits to greenhouse gas emissions needed to meet the terms of the Paris agreement. The study concludes that 2015 was likely the first time in recorded history that global temperatures were more than 1°C above pre-industrial levels. Continue reading Defining ‘pre-industrial’→
One possible criticism of global temperature datasets is that before around 1900 the observed data is too sparse to reliably infer changes in global temperature. Although we cannot travel back in time to take extra measurements to fill the gaps we can test whether the available observations are enough. Continue reading Sparse coverage of temperature observations→
There had been speculation that record low temperatures would be coming to the United States in early December, and this had been framed as either evidence against global warming in general or that cold air outbreaks are increasing due to climate change.
World Weather Attribution (WWA) presents a quantitative study of this cold air outbreak. WWA researchers compute how rare the outbreak was and how it is affected by human-caused greenhouse gases. The analysis uses the same methods as WWA used in the peer-reviewed analysis of the cold extremes in the Midwest in the winter of 2013 – 2014 (van Oldenborgh et al, 2015). Continue reading U.S. Deep Freeze, December 2016→
2016 has been quite a year for the climate. Warmest year ever recorded. Record low sea ice extents at both poles. It has also seen many amazing climate visualisations and animations. I have collected some of my favourites on this storify page, including graphics for temperature, sea ice, pressure observations and Hurricane Matthew.
One of the graphics is shown below, mapping temperature changes from 1850-2016, and including the decadal averages of global temperatures. This graphic has been updated from a previous version.