Category Archives: history

Frost fairs and the Little Ice Age

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.

Continue reading Frost fairs and the Little Ice Age

Defining ‘pre-industrial’

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’

Observing long-term climatic changes with unusual sources

We are all familiar with the usual metrics used to highlight that the climate is changing: surface air temperatures, sea level, sea surface temperatures and ocean heat content all rising, glaciers retreating, Arctic sea ice declining etc. But, there are also many other less well known sources of information about how our climate is changing, and many involve ‘citizen scientists’, who often didn’t realise the potential long-term benefits of the data they were collecting. Continue reading Observing long-term climatic changes with unusual sources

Global temperatures: 75 years after Callendar

Could varying concentrations of atmospheric carbon dioxide cause the planet to warm and cool? This was a key question facing scientists from the mid-1800s onwards – not because of a concern over man-made emissions of CO2, but because of a desire to understand the causes of the ice ages (identified by Louis Agassiz in 1837).

Then, 75 years ago, in February 1938, a little appreciated scientist, Guy Stewart Callendar, presented the first evidence that the planet had recently warmed. Callendar also suggested that changes in atmospheric CO2 had caused a large part of this observed warming. A new paper reanalyses Callendar’s work to mark the 75th anniversary of his landmark study. Continue reading Global temperatures: 75 years after Callendar