Category Archives: temperature

Defining ‘pre-industrial’

history, temperature

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’ →

Regional temperature this century

climate sensitivity, GCMs, projections, temperature

Some of the biggest questions about the future climate we have are: “how much could the climate change this century?”, “how reliable are climate projections?” and “what could happen on the way to 2100?” Also, most people want to know about regional change rather than change to the global mean climate. We have recently produced two papers relevant to these questions in terms of temperature change, now available (one on limits to temperature change this century and another on regional projections and variability).

Guest post by Michael Grose, CSIRO
Continue reading Regional temperature this century →

Lancashire temperatures, visualised

Temperatures for Lancashire from 1754-2015
Temperatures in Lancashire from 1754-2015. Click the image for a larger version.

This visualisation of temperatures in Lancashire (UK) shows annual mean data from 1754-2015. The long-term warming trend is clear, with variability from year to year, and some temporary cooler periods due to large volcanic eruptions. The average of the 19th century (black line) separates the warm and cold colours.
Continue reading Lancashire temperatures, visualised →

Reconciling estimates of climate sensitivity

climate sensitivity, GCMs, SSTs, temperature

Climate sensitivity characterises the response of the climate to changes in radiative forcing and can be measured in many different ways. However, estimates derived from observations of historical global temperatures have tended to be lower than those suggested by state-of-the-art climate simulators. Are the models too sensitive?

A new study largely explains the difference – it is because the comparison has not been done ‘like-with-like’.

The implications for understanding historical global temperature change are also significant. It is suggested that changes in global air temperature are actually ~24% larger than measured by the HadCRUT4 global temperature dataset. Continue reading Reconciling estimates of climate sensitivity →

Slowdown discussion

observations, projections, temperature, variability

The temporary slowdown in global temperatures in the early-2000s is still prompting significant scientific discussion. A recent Commentary on the topic by Fyfe et al. was summarised in an earlier post. In response, a recent post by Rahmstorf et al. reiterates some of the statistical arguments that we discussed briefly in our Commentary1, but misses the main point. Continue reading Slowdown discussion →