Category Archives: GCMs

Reliability of regional climate trends

Posted on April 15, 2013 by Ed Hawkins

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 | 3 Comments

Constraining projections with observations

Posted on February 20, 2013 by Ed Hawkins

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.

Posted in GCMs, observations, projections, temperature, uncertainty | 15 Comments

Updated comparison of simulations and observations

Posted on February 8, 2013 by Ed Hawkins

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

Posted in GCMs, observations, projections, temperature, uncertainty | 48 Comments

Visualising the role of natural variability

Posted on August 22, 2012 by Ed Hawkins

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.

Posted in GCMs, projections, temperature, uncertainty, variability, visualisation | 14 Comments

Global temperatures over the past decade

Posted on July 9, 2012 by Ed Hawkins

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.

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

Predicting changes in North Atlantic temperatures

Posted on June 28, 2012 by Jon Robson

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, … Continue reading →

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

On comparing models and observations

Posted on March 14, 2012 by Ed Hawkins

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.

Posted in GCMs, projections, uncertainty, variability | 97 Comments

What happens if you spin the Earth backwards?

Posted on December 8, 2011 by Robin Smith

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.

Posted in GCMs, MOC | 15 Comments

Time of emergence of climate signals

Posted on December 5, 2011 by Ed Hawkins

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.

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

Uncertainty in temperature variability

Posted on November 13, 2011 by Ed Hawkins

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.

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

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

Posted on September 27, 2011 by Ed Hawkins

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 … Continue reading →

Posted in GCMs, projections, temperature, uncertainty | 7 Comments

Uncertainty in uncertainty

Posted on August 24, 2011 by Ed Hawkins

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?

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

Trends in Central England Temperature

Posted on August 10, 2011 by Ed Hawkins

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.

Posted in GCMs, temperature, variability | 5 Comments

When to use uncertain climate forecasts

Posted on May 12, 2011 by Ed Hawkins

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 … Continue reading →

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

Hysteresis of the Atlantic MOC in an AOGCM

Posted on March 10, 2011 by Ed Hawkins

UPDATE (16/06/11) – the paper describing this work has now been published and highlighted. The potential for a rapid collapse in the strength of the Atlantic overturning circulation (AMOC) has long been recognised. The pioneering work of Stommel first suggested … Continue reading →

Posted in Atlantic, GCMs, hysteresis, MOC | Leave a comment

Arctic predictability

Posted on November 1, 2010 by Ed Hawkins

After attending a recent workshop on Arctic predictability, I thought a brief discussion on sea-ice variability and potential predictability might be of interest.

Posted in Arctic, GCMs, predictability, sea-ice, SSTs, variability | Leave a comment

Atlantic multi-decadal variability

Posted on August 20, 2010 by Ed Hawkins

Observations of Atlantic SSTs show significant multi-decadal variability since 1870 (see red line in figure 2 below), often termed the Atlantic Multi-Decadal Oscillation (AMO), though there is no clear evidence that it is really an ‘oscillation’.

Posted in Atlantic, GCMs, SSTs, variability | 2 Comments

Communicating climate variability

Posted on August 11, 2010 by Ed Hawkins

Update 10/03/11 – Accepted article also online. Comments very welcome. Communicating the differences and links between climate variability and climate change is of growing importance, and I am currently writing an article for “Weather” on this.

Posted in GCMs, projections, temperature, uncertainty, variability | Leave a comment

Consensus in precipitation projections

Posted on June 25, 2010 by Ed Hawkins

In the AR4, the IPCC presented this figure showing the consensus in precipitation projections for the 21st century, designed to be of use to planning for adaptation and mitigation. The coloured regions show where changes are likely to occur. My … Continue reading →

Posted in GCMs, precipitation, projections, variability | 2 Comments

Global mean temperature variability in observations and GCMs

Posted on June 24, 2010 by Ed Hawkins

I am often surprised at how different climate models can be. Shown below is the annual mean, global mean surface air temperature from control runs of 21 of the AR4 GCMs, along with the observations (HadCRUT3). The spread in the magnitude of variability is enormous, as seen by eye, but also the timeseries have very different ‘memory’ characteristics. Continue reading →

Posted in GCMs, temperature, variability | 7 Comments