Category Archives: temperature

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 | 2 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

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 | 10 Comments

The signal, the noise & the time of emergence

Temperatures have increased over most parts of the planet, but this signal is somewhat obscured by the random noisy fluctuations of natural climate variability. The year in which we can we detect the ‘signal’ of temperature change in the presence … Continue reading

Posted in emergence, observations, temperature, variability | 15 Comments

When will we reach 2°C?

A change in global surface temperature to 2°C above pre-industrial climate is often used as a threshold for ‘dangerous climate change’. Although impacts will tend to get worse as temperatures increase, there is no clear evidence yet of such a … Continue reading

Posted in emergence, observations, temperature, variability, visualisation | 4 Comments

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

The future of the slowdown

Imagine it is 2031, and the IPCC is preparing to release its 8th Assessment Report. How does the recent slowdown in global mean surface temperature rise look? As this largely depends on how fast the climate warms from 2014 onwards, … Continue reading

Posted in observations, projections, temperature, visualisation | 25 Comments

Updates to comparison of CMIP5 models & observations

As 2013 is nearly over, it is time for a short update to the comparisons of CMIP5 models and observations for global mean surface air temperatures. Part of the motivation for an update is the Cowtan & Way paper on … Continue reading

Posted in IPCC AR5, projections, temperature | 5 Comments

Effects of recent observed vs RCP forcings

The recent global temperature hiatus has been explained by the IPCC AR5 as partly due to natural radiative forcings (solar & volcanic effects) and internal variability. Recently, other effects such as CFCs and biases in the observational coverage have also … Continue reading

Posted in GCMs, projections, temperature | 4 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

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?

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?

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.

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 … 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 … 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 … 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 … 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

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.

Posted in temperature, variability, visualisation | 26 Comments