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- The well-qualified amateur who threw the spotlight back on CO2 | Simple Climate on Global temperatures: 75 years after Callendar
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- Another Week of Anthropocene Antics, May 12, 2013 – A Few Things Ill Considered on Variable variability
- HR on Variable variability
- Victor Venema on What happens if you spin the Earth backwards?
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Category Archives: GCMs
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
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.
Now that 2012 is over, it is time to update a comparison of simulations and observations of global mean temperatures.
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.
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.
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
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.
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.
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.
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.
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
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?
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.
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
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
After attending a recent workshop on Arctic predictability, I thought a brief discussion on sea-ice variability and potential predictability might be of interest.
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’.
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.
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
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