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 | 29 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 | 17 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

What happens if you spin the Earth backwards?

This might sound like a crazy idea, but bear with me. I mean, why not? We’ve got some pretty general computer models of the climate, all we have to do is change the sign of a couple of numbers. Continue reading

Posted in GCMs, MOC | 15 Comments

Time of emergence of climate signals

The time at which the signal of climate change emerges from the ‘noise’ of natural climate variability (Time of Emergence, ToE) is a key variable for climate predictions and risk assessments. Continue reading

Posted in GCMs, temperature, uncertainty, variability | 3 Comments

Uncertainty in temperature variability

It is well known that there is considerable uncertainty in the projected response of climate models to increases in radiative forcing. However, there is also considerable uncertainty in the model simulated internal variability. Continue reading

Posted in GCMs, temperature, uncertainty, variability | 1 Comment

Climate uncertainty: moving from ‘what’ to ‘when’

Update (23/10/11): The full article has now been published in Nature Climate Change

Climate projections (such as from the IPCC) usually consider the question of “what will happen to our future climate”. But, this question may be more informative if it is changed to “when will it happen”? Continue reading

Posted in GCMs, projections, temperature, uncertainty | 8 Comments

Uncertainty in uncertainty

There has been much discussion recently on whether GCMs participating in intercomparisons, such as CMIP3 and CMIP5, are ‘independent’. But if they are not, how does this make a difference to the uncertainty in our projections for future climate? Continue reading

Posted in GCMs, projections, temperature, uncertainty | 3 Comments

Trends in Central England Temperature

Previous posts have discussed climate variability in general, and modelled decadal trends in temperature specifically. However, I should have considered decadal trends in observations as well, especially as there is a long temperature record available for the UK. Continue reading

Posted in GCMs, temperature, variability | 5 Comments

Visualising climate with 2d colour bars

A recent paper by Teuling et al. suggested the use of 2d colour bars for visualising climate fields. I thought I would give this a try – and Ryan Teuling was kind enough to provide the code to construct the colour bars. Continue reading

Posted in precipitation, projections, uncertainty, visualisation | 1 Comment

Learning about past climate from ships logs

Understanding the climate of the past is extremely valuable to help put modern weather observations into a long-term context. Although we have considerable records of past weather, especially over land, more data is always welcome. Given the British obsession with the weather it is perhaps of no surprise that more data is available, it is just buried in hand-written logbooks. Transcribing this data is normally a time-consuming and expensive task…. Continue reading

Posted in Arctic, history, sea-ice, variability, weather | Leave a comment

When to use uncertain climate forecasts

Climate models produce projections of changes in climate from the present day, but these projections have a range, or spread. A simple measure of the confidence in a forecast would be the signal-to-noise ratio, r, of the size of the projected change to the spread around that change. An important question is ‘when does the spread in the forecasts become so large that the forecast should not be used’? Continue reading

Posted in GCMs, precipitation, projections, uncertainty | Leave a comment

What is a year?

A rather surprising question perhaps, but the answer is, ‘it depends’. There is no climatic reason to define a year from January to December, but that is what is generally done. But, is this the best definition? Continue reading

Posted in SSTs, temperature, variability | 3 Comments