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 up to 2050, but with a specific focus on the 2016-2035 period.

Continue reading Near-term global surface temperature projections in IPCC AR5

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 a local warming or cooling? Continue reading Near-term regional climate: the range of possibilities

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) recent changes need to be put in longer term context & other climate indicators such as sea level, Arctic sea ice, snow cover, glacier melt etc are also important; (2) the explanation for recent slowdown is partly additional ocean heat uptake & partly negative trends in natural radiative forcing (due to solar changes and small volcanic eruptions) which slightly counteract the positive forcing from GHGs; (3) the quantification of the relative magnitude of these causes is still work in progress; (4) climate models simulate similar pauses. Continue reading Recent slowdown in global surface temperature rise

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 misinterpretation of this comparison, often without the correct attribution or links to the original source, a more complete description & update is needed. Continue reading Comparing global temperature observations and simulations, again

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 desire to understand the causes of the ice ages (identified by Louis Agassiz in 1837).

Then, exactly 75 years ago, in April 1938, a little appreciated scientist, Guy Stewart Callendar, presented the first evidence that the planet had recently warmed. Callendar also suggested that changes in atmospheric CO2 had caused a large part of this observed warming. A new paper reanalyses Callendar’s work to mark the 75th anniversary of his landmark study. Continue reading Global temperatures: 75 years after Callendar

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 of greenhouse gases do not diverge much and we could work towards climate forecasts: calibrated probability distributions of the climate in the future. Continue reading Reliability of regional climate trends

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 Arctic sea ice in 2013

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 Predicting changes in North Atlantic temperatures

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 Reconstructing Atlantic atmospheric variability

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