2015 was hot. Globally, it was the warmest year on record by a large margin. But, there was an El Nino event in the Pacific which probably boosted temperatures slightly (by up to 0.1°C).
So, what can we expect for 2016? Using an analogy of similar El Nino events we can make some suggestions. Continue reading Expectations for 2016 global temperatures
2015 has seen some significant climate events, both meteorological and political. Continue reading 2015 in review
The Paris COP21 continues. The atmosphere today was far more relaxed after the excitement of the speeches from world leaders yesterday. Negotiations have started more seriously with discussions over decarbonisation – perhaps this should be called carbon austerity! Continue reading Reflections from Paris COP – day 2
How will global temperatures evolve over the next 20 years? The IPCC AR5 made an assessment that average global temperatures in the 2016-2035 period would likely be 0.3 – 0.7°C above the 1986-2005 average. Some climate scientists disagree with that assessment. Continue reading Near-term global temperature forecasts
In Weather this month, a paper by Colin Clark discusses temperature data from two rural stations in Somerset (UK). These two stations show a cooling trend over the last two decades which Clark suggests is opposite to that expected. The associated editorial suggests that this is a controversial finding.
Continue reading Comment on Clark (2015)
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?
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’?
The slower warming of global temperatures in the early 2000s has motivated many papers examining the modulation of global trends by climate variability. One question that has emerged is: what happens after a pause? Continue reading Are pauses followed by surges?
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
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
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
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
An update to the NOAA global temperature estimates has generated a lot of media excitement, based on a paper by Karl et al. in Science. How do the new estimates compare with other global temperature timeseries? Continue reading Global temperature comparisons
The largest impacts of increases in temperature will not be experienced due to changes in the mean, but by changes in the extremes. This is illustrated using UK heatwaves to show that the number of days which will require preventative action will increase by roughly a factor of 6 for a 2ºC increase in summer temperatures. Continue reading Extreme UK heatwaves
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