The Coordinated Regional Climate Downscaling Experiment (CORDEX), an initiative of the World Meteorological Organization is now able to render the data from regional climate models to the scale people live in, and decision makers work at. The information will not only help countries but also communities in their efforts to adapt to changing weather patterns, and to tailor their disaster risk reduction plans.
The effort is geared to feed into the next assessment report of the Intergovernmental Panel on Climate Change (IPCC), due to be released in 2014.
Although CORDEX aims to “downscale” the data for all regions of the world, Africa has been identified as the most vulnerable by the IPCC and a priority for the initiative. Historically the continent has been under-researched, but for the next two years will be a focus for the programme.
Chris Lennard, a scientist at the Climate Systems Analysis Group at the University of Cape Town (UCT) in South Africa, which has one of the only two climate modelling groups downscaling the projections in Africa, said by mid-2012 climate data for people living within 50 kilometres from each other will be available across Africa.
The other African group, also in South Africa, is based at the Council for Scientific and Industrial Research (CSIR) in Pretoria.
“There are climatologists outside the project who are downscaling up to a 22 km resolution as well,” said Lennard. “Although this means data at the scale of cities will be available, when assessing vulnerabilities to climate change in a place like Johannesburg there are many other factors that need to be considered external to the city, such as water and food security and power provision, for example.”
How it works
Projecting the impact of climate change is a complicated process that takes into account changes in the long-term averages of daily weather patterns and many other factors. Climate models are used to simulate processes that occur in the atmosphere, such as the movement of moisture and heat as well as the possible impact of increasing concentrations of greenhouse gases on these processes.
During two meetings in 2011, over 20 African climate scientists met to analyse CORDEX produced data. They decided to divide Africa into three regions for analysis – Southern, East and West. They then sub-divided the regions according to the common characteristics of the rainfall patterns in them. For instance, West Africa has been split into a Southern and Northern region because the south has two peaks per rainy season and the north has only one.
Climatologists often split regions according to common rainfall patterns because the variables that affect rainfall – movement of air, pressure, temperature, radiation, moisture content – also drive climate change.
Unfortunately, not all African countries can be assessed because of a lack of adequate scientific support and observational data.
So, for example, model-based physical impacts in the Netherlands look similar to those in Bangladesh – in part because the two countries share a similar topography, both being low-lying deltas – but in reality the impacts on people, and the options for adapting to these, are likely to differ widelyDuring the first stage of CORDEX, scientists tested the ability of the various regional climate models to generate data based on actual climate statistics for the period 1988-2010. “The selected historical timeframe is too small to look at any long-term trends,” said Lennard. “We wanted to see how the regional climate models simulated the past so we can say something about how they might simulate the future.”
The 14 regional climate models also include factors like the level of small-scale convection, and the interaction between the land surface and the atmosphere. The scientists then work on a consensus position based on the results generated by all the models.
“We have completed this stage and are busy writing up our results so they can be included in the IPCC 5th assessment report,” said Lennard.
The teams are now awaiting results of global projections of climate change from 12 global climate modelling groups already at work in Europe, the US and elsewhere.
These groups – including the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy; the Swedish Meteorological and Hydrological Institute; the Danish Meteorological Institute; and the Iowa State University – are among the world’s foremost global climate modelling institutions. They have simulated the earth’s climate as far back as 1950 and look as far forward as 2100.
“Once the global climate model data become available we will start downscaling them, and the downscaled results will be shared with the African teams for analysis. We expect to have the first downscaled model data early in November,” Lennard said.
Making sense of the numbers
The projections are critical for communities that must adapt to a moodier climate with limited resources. Initial IPCC assessment reports tended to focus on global climate models and predictions that did not factor in underlying socioeconomic conditions or the vulnerability of communities, writes Saleemul Huq, one of the IPCC’s lead authors.
“So, for example, model-based physical impacts in the Netherlands look similar to those in Bangladesh – in part because the two countries share a similar topography, both being low-lying deltas – but in reality the impacts on people, and the options for adapting to these, are likely to differ widely,” Huq notes in a briefing paper for the International Institute for Environment and Development (IIED).
Climate change in-depth “The Netherlands is technologically and financially rich and can adapt to rising sea levels by raising dykes. Bangladesh, on the other hand, cannot afford to build dykes around its entire coast, even if that was the best adaptation solution.” More recent IPCC reports have gone for a “more rounded picture of which countries and regions are at highest risk from climate change”.
One of the unique characteristics of the CORDEX Africa campaign is that African climatologists will meet with other African scientists who study vulnerability, adaptation and the impact of climate change on people, to translate the model numbers into meaningful, usable information. Experts from countries that include Benin, Burkina Faso, Ethiopia, Ghana, Kenya, Malawi, Niger, Nigeria, Senegal, South Africa, Swaziland, Uganda, Zambia and Zimbabwe will analyse the data.
“These scientists [who study humanitarian impact of climate change] know for example what thresholds, which, if crossed more frequently would impact detrimentally on communities, so whether the people in a certain area are more vulnerable to five days or eight days of continuous rainfall,” said Lennard.
“We are coming together so that the impacts scientists can ask climatologists their questions, who will then analyse the model output with these questions in mind and provide them with information they can use.”
Their answers will also inform the analysis included in the IPCC’s fifth assessment, which is devoting four chapters to adaptation. The previous report, in 2007, carried just one chapter on the topic.