Four Degrees

In this blog we don’t spend a great deal of time on climate change/global warming. This is not because we do not believe it’s a problem – it is. But in the larger picture of what is happening in God’s creation, climate change is one of many problems, including loss of biodiversity (extinctions), water, deforestation, chemical pollution – the list could go on and on. The January issue of the Journal of the Royal Geographic Society, one of the most prestigious scientific organizations in the world, devotes itself to the question of whether and when the globe might reach a temperature increase of four degrees Celsius (7 degrees F) and what such a temperature rise might mean. This is not good bedtime reading, but you need to at least take a look.

Here is a list of some of the articles in this issue with a quote or two from each. The content is free today – I’m not sure if it will remain so. I have copies if the links to the articles no longer work – drop a note in the comments or send me a message.

When could global warming reach 4°C?

The A1FI emissions scenario would lead to a rise in global mean temperature of between approximately 3°C and 7°C by the 2090s relative to pre-industrial, with best estimates being around 5°C. Our best estimate is that a temperature rise of 4°C would be reached in the 2070s, and if carbon-cycle feedbacks are strong, then 4°C could be reached in the early 2060s—this latter projection appears to be consistent with the upper end of the IPCC’s likely range of warming for the A1FI scenario.

Regional temperature and precipitation changes under high-end (≥4^°C) global warming

[Note: The point in this paper is that 4 degree warming globally will very likely produce a number of ‘hotspots’ where regional warming is much greater than 4 degrees. Also keep in mind that all temps are in Celsius…]

Under the high-end models, Northern Africa is projected to experience high (greater than 6^°C) temperature increases and large precipitation decreases in both DJF and JJA, suggesting that this region is most at risk from high-end climate change. In addition, during JJA, Southern Europe and the adjacent part of Central Asia are projected to warm by 6–8^°C, together with a decrease in precipitation of 10 per cent or more. This result suggests that drier soils, a consequence of the reduced precipitation, are the cause of the elevated temperatures, as the evaporative cooling effect will be smaller.

Water availability in +2°C and +4°C worlds

In a +2°C world, population growth in most large river basins tends to override climate change as a driver of water stress, while in a +4°C world, climate change becomes more dominant, even compensating for population effects where climate change increases run-off. However, in some basins where climate change has positive effects, the seasonality of surface run-off becomes increasingly amplified in a +4°C climate.

…changes in mean annual run-off in a +2°C world are generally amplified in a +4°C world: drier areas dry further and wetter areas become wetter.

By examining a subset of the world’s major river basins, we have shown that the picture for water stress in each river basin is dependent on the magnitude of the climate change and the nature of the population growth. For some river basins, the effects of climate change become large enough to offset the large increases in demand in a +4°C world, e.g. in the Ganges; in most basins, however, climate and population growth combine to increase stress or climate change is insufficient to offset increased demand.

Agriculture and food systems in sub-Saharan Africa in a 4^°C+ world

Agricultural development in sub-Saharan Africa faces daunting challenges, which climate change and increasing climate variability will compound in vulnerable areas. The impacts of a changing climate on agricultural production in a world that warms by 4^°C or more are likely to be severe in places. The livelihoods of many croppers and livestock keepers in Africa are associated with diversity of options. The changes in crop and livestock production that are likely to result in a 4^°C+ world will diminish the options available to most smallholders. In such a world, current crop and livestock varieties and agricultural practices will often be inadequate, and food security will be more difficult to achieve…

Sea-level rise and its possible impacts given a ‘beyond 4°C world’ in the twenty-first century

The range of future climate-induced sea-level rise remains highly uncertain with continued concern that large increases in the twenty-first century cannot be ruled out. The biggest source of uncertainty is the response of the large ice sheets of Greenland and west Antarctica. Based on our analysis, a pragmatic estimate of sea-level rise by 2100, for a temperature rise of 4°C or more over the same time frame, is between 0.5 m and 2 m—the probability of rises at the high end is judged to be very low, but of unquantifiable probability. However, if realized, an indicative analysis shows that the impact potential is severe, with the real risk of the forced displacement of up to 187 million people over the century (up to 2.4% of global population).

Climate-induced population displacements in a 4^°C+ world

In the event of a 4^°C+ warming, not only is it likely that climate-induced population movements will be more considerable, but also their patterns could be significantly different, as people might react differently to temperature changes that would represent a threat to their very survival. This paper puts forward the hypothesis that a greater temperature change would affect not only the magnitude of the associated population movements, but also—and above all—the characteristics of these movements, and therefore the policy responses that can address them.

Population movements associated with climate change impacts are expected to take place mostly at the internal level, over short distances, and eventually on a permanent basis. Overall, it appears that the most significant impact of a 4^°C+ warming on migration would be to reduce populations’ ability to move on their own terms, as many people would no longer have the choice to stay or to leave when confronted with environmental changes.

On the other hand…

Climate-induced migration should be addressed not only within the framework of climate change, but also within the discussions on the global governance of migration. In many cases, migration does not have to be envisioned as a humanitarian catastrophe, but can also be a solution to environmental disruption, which would allow people to relocate into safer areas and to cope better with climate change impacts.

Rethinking adaptation for a 4^°C world

With weakening prospects of prompt mitigation, it is increasingly likely that the world will experience 4^°C and more of global warming. In such a world, adaptation decisions that have long lead times or that have implications playing out over many decades become more uncertain and complex. Adapting to

In this blog we don’t spend a great deal of time on climate change/global warming.  This is not because we do not believe it’s a problem – it is.  But in the larger picture of what is happening in God’s creation, climate change is one of many problems, including loss of biodiversity (extinctions), water, deforestation, chemical pollution – the list could go on and on. The January issue of the Journal of the Royal Geographic Society, one of the most prestigious scientific organizations in the world, devotes itself to the question of whether and when the globe might reach a temperature increase of four degrees Celsius (7 degrees F) and what such a temperature rise might mean.  This is not good bedtime reading, but you need to at least take a look.

Here is a list of some of the articles in this issue with a quote or two from each.  The content is free today – I’m not sure if it will remain so.  I have copies if the links to the articles no longer work – drop a note in the comments or send me a message.

When could global warming reach 4°C?

The A1FI emissions scenario would lead to a rise in global mean temperature of between approximately 3°C and 7°C by the 2090s relative to pre-industrial, with best estimates being around 5°C. Our best estimate is that a temperature rise of 4°C would be reached in the 2070s, and if carbon-cycle feedbacks are strong, then 4°C could be reached in the early 2060s—this latter projection appears to be consistent with the upper end of the IPCC’s likely range of warming for the A1FI scenario.

Regional temperature and precipitation changes under high-end (≥4^°C) global warming

[Note: The point in this paper is that 4 degree warming globally will very likely produce a number of ‘hotspots’ where regional warming is much greater than 4 degrees.  Also keep in mind that all temps are in Celsius…]

Under the high-end models, Northern Africa is projected to experience high (greater than 6^°C) temperature increases and large precipitation decreases in both DJF and JJA, suggesting that this region is most at risk from high-end climate change. In addition, during JJA, Southern Europe and the adjacent part of Central Asia are projected to warm by 6–8^°C, together with a decrease in precipitation of 10 per cent or more. This result suggests that drier soils, a consequence of the reduced precipitation, are the cause of the elevated temperatures, as the evaporative cooling effect will be smaller.

Water availability in +2°C and +4°C worlds

In a +2°C world, population growth in most large river basins tends to override climate change as a driver of water stress, while in a +4°C world, climate change becomes more dominant, even compensating for population effects where climate change increases run-off. However, in some basins where climate change has positive effects, the seasonality of surface run-off becomes increasingly amplified in a +4°C climate.

…changes in mean annual run-off in a +2°C world are generally amplified in a +4°C world: drier areas dry further and wetter areas become wetter.

By examining a subset of the world’s major river basins, we have shown that the picture for water stress in each river basin is dependent on the magnitude of the climate change and the nature of the population growth. For some river basins, the effects of climate change become large enough to offset the large increases in demand in a +4°C world, e.g. in the Ganges; in most basins, however, climate and population growth combine to increase stress or climate change is insufficient to offset increased demand.

Agriculture and food systems in sub-Saharan Africa in a 4^°C+ world

Agricultural development in sub-Saharan Africa faces daunting challenges, which climate change and increasing climate variability will compound in vulnerable areas. The impacts of a changing climate on agricultural production in a world that warms by 4^°C or more are likely to be severe in places. The livelihoods of many croppers and livestock keepers in Africa are associated with diversity of options. The changes in crop and livestock production that are likely to result in a 4^°C+ world will diminish the options available to most smallholders. In such a world, current crop and livestock varieties and agricultural practices will often be inadequate, and food security will be more difficult to achieve…

Sea-level rise and its possible impacts given a ‘beyond 4°C world’ in the twenty-first century

The range of future climate-induced sea-level rise remains highly uncertain with continued concern that large increases in the twenty-first century cannot be ruled out. The biggest source of uncertainty is the response of the large ice sheets of Greenland and west Antarctica. Based on our analysis, a pragmatic estimate of sea-level rise by 2100, for a temperature rise of 4°C or more over the same time frame, is between 0.5 m and 2 m—the probability of rises at the high end is judged to be very low, but of unquantifiable probability. However, if realized, an indicative analysis shows that the impact potential is severe, with the real risk of the forced displacement of up to 187 million people over the century (up to 2.4% of global population).

Climate-induced population displacements in a 4^°C+ world

In the event of a 4^°C+ warming, not only is it likely that climate-induced population movements will be more considerable, but also their patterns could be significantly different, as people might react differently to temperature changes that would represent a threat to their very survival. This paper puts forward the hypothesis that a greater temperature change would affect not only the magnitude of the associated population movements, but also—and above all—the characteristics of these movements, and therefore the policy responses that can address them.

Population movements associated with climate change impacts are expected to take place mostly at the internal level, over short distances, and eventually on a permanent basis. Overall, it appears that the most significant impact of a 4^°C+ warming on migration would be to reduce populations’ ability to move on their own terms, as many people would no longer have the choice to stay or to leave when confronted with environmental changes.

On the other hand…

Climate-induced migration should be addressed not only within the framework of climate change, but also within the discussions on the global governance of migration. In many cases, migration does not have to be envisioned as a humanitarian catastrophe, but can also be a solution to environmental disruption, which would allow people to relocate into safer areas and to cope better with climate change impacts.

Rethinking adaptation for a 4^°C world

With weakening prospects of prompt mitigation, it is increasingly likely that the world will experience 4^°C and more of global warming. In such a world, adaptation decisions that have long lead times or that have implications playing out over many decades become more uncertain and complex. Adapting to global warming of 4^°C cannot be seen as a mere extrapolation of adaptation to 2^°C; it will be a more substantial, continuous and transformative process.

…We therefore show how it is possible to systematize an approach to the resulting decision-making challenges in ways that have the potential to reduce the disempowering impacts of uncertainty, by disaggregating the decision-making process into actionable steps that use well-established methodologies. To do this, we have shown how the lifetime of a decision interacts with the different types of uncertainty and the nature of potential adaptation responses. The resulting six categories of decision pathways require distinctive risk-management strategies and tactics, all of which are individually well understood.

global warming of 4^°C cannot be seen as a mere extrapolation of adaptation to 2^°C; it will be a more substantial, continuous and transformative process.

…We therefore show how it is possible to systematize an approach to the resulting decision-making challenges in ways that have the potential to reduce the disempowering impacts of uncertainty, by disaggregating the decision-making process into actionable steps that use well-established methodologies. To do this, we have shown how the lifetime of a decision interacts with the different types of uncertainty and the nature of potential adaptation responses. The resulting six categories of decision pathways require distinctive risk-management strategies and tactics, all of which are individually well understood.