Category Archives: temperature

What have global temperatures ever done for us?

Much attention is rightly given to changes in global mean surface temperature – it is the key metric for assessing how our climate is changing and evaluating mitigation strategies. However, no-one directly experiences changes in global mean temperature – it is only through local variations that changes in climate are felt.

So, what have global temperatures ever done for us? Continue reading What have global temperatures ever done for us?

Was there ever a ‘pause’?

The importance of the ‘pause’ in global temperatures has never been about whether some particular trend is just below or just above zero, or about whether a specific period shows a statistically significant trend (whatever that actually means), or even about whether the trend has changed. The ‘pause’ has always been about understanding whether Earth’s climate is evolving in line with our expectations. Continue reading Was there ever a ‘pause’?

An apples to apples comparison of global temperatures

When comparing global temperatures estimated from observations with climate model simulations it is necessary to compare ‘apples with apples’. Previous posts have discussed the issues of incomplete observational data, but a new paper by Cowtan et al. quantifies the influence of different observational data types. Continue reading An apples to apples comparison of global temperatures

Back-of-the-envelope attribution of global temperature changes

Many of those skeptical about the causes of climate change suggest that the complex global climate models (GCMs) often used to make attribution statements are not trustworthy. Here I highlight that GCMs are not needed to roughly attribute nearly all of the observed warming (at least) to changes in greenhouse gases. Continue reading Back-of-the-envelope attribution of global temperature changes

A spectrum of global temperature trends

Trends in global mean temperature are not static through time. Changes due to radiative forcings are influenced by internal climate variability. A recent paper by Karl et al. concluded that:

the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a “slowdown” in the increase of global surface temperature.

Are these conclusions, based on comparing a few periods, correct? Continue reading A spectrum of global temperature trends

How not to use daily CMIP5 data for impact studies

A new paper out this week in PLOS Biology uses some CMIP5 simulations of daily mean surface air temperature as part of a larger analysis on the change to future plant growing days. The description of the analysis suggests they have not used the simulations appropriately to arrive at their conclusions. Here I highlight a couple of possible pitfalls in using such data in impact studies. Continue reading How not to use daily CMIP5 data for impact studies

Hiatus delays unprecedented warming rates

Current global temperatures are often discussed in terms of their unprecedented nature when compared to the last few thousand years. An interesting paper in Nature Climate Change by Steven J Smith and colleagues examines the rate of warming projected by the CMIP5 ensemble and suggests that the rate of warming is unprecedented also. However, we note here that their projections are not constrained by the current observations which do not show such strong warming rates at present, and are unlikely to do so in the next few years. Continue reading Hiatus delays unprecedented warming rates