Category Archives: variability

Visualising UK summer temperatures – what are the odds?

How will UK summer temperatures change in future? And, how might we best communicate the possibilities? This is a short post describing one effort in visualising the possible outcomes.

Posted in observations, projections, temperature, uncertainty, variability, visualisation | 2 Comments

Top-of-atmosphere contribution to unforced variability in global temperature

As the attention received by the ‘global warming hiatus’ demonstrates, global mean surface temperature (T) variability on decadal timescales is of great interest to both the general public and to scientists. Here, I will discuss a recently published paper (Brown … Continue reading

Posted in GCMs, observations, temperature, uncertainty, variability | 5 Comments

More Mora emergence issues

A previous post discussed the recent Comment on Mora et al., which considered mainly methodological & statistical errors. However, the erroneous assumptions regarding uncertainty in the Mora et al. study have further implications for their results on population and income. … Continue reading

Posted in emergence, GCMs, projections, uncertainty, variability | 2 Comments

On Mora et al.’s Reply

Yesterday saw the publication of our Comment on Mora et al., along with Mora et al.’s Reply and an associated ‘News & Views’ piece. Although the Editors deserve credit for commissioning a News & Views piece on this exchange – … Continue reading

Posted in climate sensitivity, emergence, journals, uncertainty, variability | 17 Comments

Uncertainties in the timing of unprecedented climates

Back in October 2013, Nature published an analysis by Camilo Mora et al. which discussed when ‘unprecedented climates’ would emerge, with a focus on regions of high biodiversity. The paper was highlighted by Nature with an associated News & Views … Continue reading

Posted in emergence, GCMs, IPCC AR5, projections, temperature, uncertainty, variability | 10 Comments

The signal, the noise & the time of emergence

Temperatures have increased over most parts of the planet, but this signal is somewhat obscured by the random noisy fluctuations of natural climate variability. The year in which we can we detect the ‘signal’ of temperature change in the presence … Continue reading

Posted in emergence, observations, temperature, variability | 15 Comments

Predictable September Arctic sea-ice minimum?

Arctic sea-ice extent varies considerably from year-to-year, especially in the summer. Skillful forecasts of the expected extent could be valuable to a wide range of Arctic stakeholders. But, how predictable is the Arctic sea-ice extent in summer? And, can more … Continue reading

Posted in Arctic, predictability, sea-ice, variability | 4 Comments

When will we reach 2°C?

A change in global surface temperature to 2°C above pre-industrial climate is often used as a threshold for ‘dangerous climate change’. Although impacts will tend to get worse as temperatures increase, there is no clear evidence yet of such a … Continue reading

Posted in emergence, observations, temperature, variability, visualisation | 4 Comments

Demonstrating climate variability

Communicating climate variability has become an important issue with the recent slowdown in global surface temperature rise. Below are some examples of different aspects of communicating these issues, with a focus on regional spatial scales, but more examples would be … Continue reading

Posted in variability, visualisation | 11 Comments

The cascade of uncertainty in climate projections

Climate projections have demonstrated the need to adapt to a changing climate, but have been less helpful (so far) in guiding how to effectively adapt. Part of the reason is the ‘cascade of uncertainty’ going from assumptions about future global … Continue reading

Posted in projections, temperature, uncertainty, variability, visualisation | 11 Comments

Atlantic overturning in decline?

Recent direct observations of the strength of the Atlantic Meridional Overturning Circulation (AMOC) show a decline of 10-15% since 2004. Is this a temporary fluctuation or part of a longer-term decline? A new analysis suggests that we might expect a … Continue reading

Posted in Atlantic, MOC, observations, variability | 4 Comments

The future of white Christmases

It’s December, which means the usual discussion as to whether or not it will be a white Christmas. You can even bet on it. But, how might these odds change in future? Are children going to know what snow is?

Posted in projections, variability, weather | 2 Comments

Sources of uncertainty in CMIP5 projections

The recent IPCC AR5 includes a discussion on the sources of uncertainty in climate projections (Fig. 11.8, section 11.3.1.1), which updates previous analyses using CMIP3 (temperature, precipitation) to the latest CMIP5 simulations. The dominant source of uncertainty depends on lead … Continue reading

Posted in GCMs, IPCC AR5, projections, temperature, uncertainty, variability, visualisation | 13 Comments

Near-term global surface temperature projections in IPCC AR5

The final version of the IPCC AR5 WG1 assessment on the physical basis for climate change has now been published. The AR5 includes, for the first time, a specific chapter and assessment on ‘near-term’ climate change, which covers the period … Continue reading

Posted in IPCC AR5, projections, temperature, uncertainty, variability | 25 Comments

Near-term regional climate: the range of possibilities

What are the possible regional temperature trends over the coming few decades? Globally, on average, there is expected to be a long-term warming, but this is not necessarily true for any particular location or period. What are the probabilities of … Continue reading

Posted in GCMs, projections, temperature, uncertainty, variability, visualisation | 10 Comments

Recent slowdown in global surface temperature rise

The Science Media Centre recently held a briefing for journalists on the recent slowdown in global surface temperature rise, and published an accompanying briefing note. The Met Office also released three reports on the topic. The key points were: (1) … Continue reading

Posted in observations, temperature, uncertainty, variability, visualisation | 11 Comments

Lengthy simulated pauses in global mean surface temperature

A very simple question for this short post: what length pause (trend < 0) in global mean surface temperature could be simulated in a warming climate?

Posted in GCMs, temperature, variability | 19 Comments

Rates of change in global temperatures

The recent WMO press release on the climate of the 2001-2010 period highlighted that global temperature change was accelerating. Although this could be a misleading statement, should we even be expecting global temperature changes to be accelerating at present?

Posted in GCMs, observations, projections, temperature, uncertainty, variability | 6 Comments

Comparing global temperature observations and simulations, again

A recent comparison of global temperature observations and model simulations on this blog prompted a rush of media and wider interest, notably in the Daily Mail, The Economist & in evidence to the US House of Representatives. Given the widespread … Continue reading

Posted in observations, projections, temperature, uncertainty, variability | 43 Comments

Variable variability

The latest global climate models (GCMs) have performed pre-industrial control simulations as part of the CMIP5 coordinated experiments. In these simulations there are no changes to radiative forcings, which are kept fixed at year 1850 values – all the variability … Continue reading

Posted in temperature, variability | 3 Comments

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 … Continue reading

Posted in history, observations, temperature, variability | 24 Comments

Reliability of regional climate trends

Climate information for the future is usually presented in the form of scenarios: plausible and consistent descriptions of future climate without probability information. This suffices for many purposes, but for the near term, say up to 2050, scenarios of emissions … Continue reading

Posted in GCMs, observations, projections, temperature, uncertainty, variability | 4 Comments

What will the simulations do next?

Recent conversations on the recent slowdown in warming has inspired an animation on how models simulate this phenomenon, and what it means for the evolution of global temperatures over the next few decades.

Posted in temperature, variability, visualisation | 26 Comments

Months since below average temperatures

NOAA have recently been promoting that November 2012 was the 333rd month in a row with above average global temperatures, and this has been widely picked up by the media (e.g. here). But, how useful is this statistic?

Posted in temperature, variability | 9 Comments

Temperatures in Mongolia

I was alerted to an article on climate change in Mongolia which claims that temperatures there have already risen by more than 2C since the 1940s. A few minutes on Climate Explorer allowed me to check.

Posted in history, temperature, variability | 4 Comments