Category Archives: uncertainty

Earth’s energy imbalance

Global surface air temperatures have risen less rapidly over the past 15 years than the previous few decades. The causes of this ‘hiatus’ have been much debated. However, just considering surface temperatures does not tell the whole story – a … Continue reading

Posted in communication, energy balance, GCMs, uncertainty | 14 Comments

Wet get drier (eventually)?

A prevailing paradigm of how rainfall patterns will change on a warming Earth is that the hydrological cycle strengthens causing wet regions to get wetter and dry regions to get drier. However, this is not always the case: Hawkins, Joshi … Continue reading

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

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 | 7 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 | 11 Comments

Improving the weather from 96 years ago

Ideally, we would have observations of past weather everywhere for several centuries to reconstruct the state of the atmosphere and learn about its variability. But, we don’t. Instead, all the observations ever taken would, ideally, be available digitally for everyone … Continue reading

Posted in observations, uncertainty, weather | Leave a comment

Comments on the GWPF climate sensitivity report

Guest post by Piers Forster, with comments from Jonathan Gregory & Ed Hawkins Lewis & Crok have circulated a report, published by the Global Warming Policy Foundation (GWPF), criticising the assessment of equilibrium climate sensitivity (ECS) and transient climate response … Continue reading

Posted in climate sensitivity, GCMs, IPCC AR5, observations, projections, temperature, uncertainty | 223 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

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

Time of emergence of a warming signal

The ‘signal’ of a warming climate is emerging against a background ‘noise’ of natural internal variability. Both the magnitude of the signal and the noise vary spatially and seasonally. As society and ecosystems tend to be somewhat adapted to natural … Continue reading

Posted in emergence, GCMs, IPCC AR5, projections, temperature, uncertainty | 11 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

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 | 44 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

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.

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.

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

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

Projections of maize yields in France

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

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

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

Posted in uncertainty | 14 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.

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