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?

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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? Continue reading

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

Global temperature changes in WMO report

A recent press release by the World Meteorological Organisation (WMO) described recent global temperature changes, and highlighted extreme weather in the 2001-2010 period. Much of the press release is good, but here I will examine the accuracy of two statements. Continue reading

Posted in temperature | 19 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 misinterpretation of this comparison, often without the correct attribution or links to the original source, a more complete description & update is needed. 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 is therefore generated internally to the climate system. How different can this variability be? 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 desire to understand the causes of the ice ages (identified by Louis Agassiz in 1837).

Then, exactly 75 years ago, in April 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

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 of greenhouse gases do not diverge much and we could work towards climate forecasts: calibrated probability distributions of the climate in the future. Continue reading

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

Constraining projections with observations

Can past observations be used to help constrain future temperature projections? This question is particularly relevant given the last decade which has shown relatively less warming than expected. Continue reading

Posted in GCMs, observations, projections, temperature, uncertainty | 17 Comments

Updated comparison of simulations and observations

Now that 2012 is over, it is time to update a comparison of simulations and observations of global mean temperatures.

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Posted in GCMs, observations, projections, temperature, uncertainty | 54 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. Continue reading

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? Continue reading

Posted in temperature, variability | 9 Comments

Predictions of the past & the future

What will happen to the climate over the next decade? Two new analyses consider real climate predictions made in the past and of the future decade. Continue reading

Posted in predictability, temperature | 6 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. Continue reading

Posted in history, temperature, variability | 4 Comments

How “weird” has UK weather been in 2012?

A recent article on the BBC website said:

The UK has experienced its “weirdest” weather on record in the past few months, scientists say.

The question today is then, is this true? Continue reading

Posted in history, precipitation, variability, weather | 6 Comments

Arctic sea ice in 2013

A very simple straw poll today – will the Arctic sea ice extent in September 2013 be more or less than September 2012? Hoping for views and expectations from public and scientists alike.

UPDATE: (06/09/12)
Around 80% of the ~100 scientists at the Bjerknes conference thought that there would be MORE Arctic sea-ice in 2013, compared to 2012. Around 40% of the ‘public’ thought there would be more (but small sample of 10!). Continue reading

Posted in Arctic, predictability, variability | 30 Comments

Visualising the role of natural variability

A new analysis by Clara Deser and colleagues (accepted for Nature Climate Change), provides some fantastic visualisations of the crucial role of natural variability in how we will experience climate. Continue reading

Posted in GCMs, projections, temperature, uncertainty, variability, visualisation | 18 Comments

Global temperatures over the past decade

It is well known that the past decade or so has seen less global warming than might have been expected – but what is the cause? This is more of a discussion post, rather than any new analysis. Continue reading

Posted in GCMs, projections, temperature, variability | 31 Comments

Predicting changes in North Atlantic temperatures

The Earth is a complex system of interacting components, such as the atmosphere and ocean, which produce a wide variety of natural variability. This natural variability ensures that the evolution of a particular region’s climate, e.g. that of Western Europe, could be completely different to another region, or indeed the global mean climate. Such variability can impact on many areas of society; for example winter energy usage, or agriculture in sensitive regions. Continue reading

Posted in Atlantic, GCMs, MOC, predictability, SSTs, variability | 1 Comment

Projections of maize yields in France

A rather specific question today – what will happen to maize yields in France in 2016-2035? Continue reading

Posted in crops, precipitation, projections, temperature, uncertainty, variability | 5 Comments

A 150 year temperature history from Berkshire

At a recent weather festival, Roger Brugge presented a reconstruction of temperatures from 1863 to 2011 for a small patch of the UK, namely Berkshire, which I found interesting. Continue reading

Posted in history, temperature | 8 Comments

Nice climate figures

“A picture is worth a thousand words”, says the popular adage. It is something that we, as climate scientists, should take seriously, especially given the vast quantities of literature we might read through. Continue reading

Posted in visualisation | 2 Comments

On comparing models and observations

There has been some recent blog discussion on comparing observations and climate models consistently. Here is my effort at such a comparison using the CMIP5 models which are already available. Continue reading

Posted in GCMs, projections, uncertainty, variability | 98 Comments

The value of old weather observations

Previous posts have described some initial analysis of the data from the Old Weather project, which is using public volunteers to digitise new historical weather observations from Royal Navy ships during World War 1. The good news is that these observations will improve our knowledge of the atmospheric circulation. Continue reading

Posted in history, variability, weather | Leave a comment

Reconstructing Atlantic atmospheric variability

In a previous post I discussed the Old Weather project which is using volunteers to transcribe the hand-written weather data from Royal Navy ships logs in the World War 1 period. The good news is the first 243 ships have been completed (providing data scattered throughout the period 1914-1923), and some simple analysis shows whether this data can help reconstruct past Atlantic atmospheric variability. Continue reading

Posted in Atlantic, history, variability, weather | 4 Comments

The importance of reliable uncertainty estimates

Reliable estimates of uncertainty are arguably more important than the actual value being quoted. I recently came across a classic example in astronomy. Continue reading

Posted in uncertainty | 14 Comments