Page 10 - Respond 2019 Magazine
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       Pathways to 1.5C
       18.   To keep to 1.5C, CO2 emissions would have to decline by   uncertainties”, “knowledge gaps”, “substantial risks” and
          about 45% between 2010 and 2030 and hit net zero in 2050.   “institutional and social constraints”.
          That’s significantly faster than what is needed for 2C – a   24.  The biggest polluting industries will have to make radical
          reduction of around 20% by 2030 and net zero by 2075.
                                                               changes. In energy, renewables will need to supply 70% to 85%
       19.   Methane and black carbon, both more potent greenhouse   of power by 2050. There is still room for fossil fuel generation
          gases, will need to be cut by at least 35% by 2050, compared   combined with technology to catch and store CO2 emissions,
          to 2010. But cuts in non-CO2 emissions must be made   but it’s small: around 8% for gas and close to zero for coal by
          carefully. If more bioenergy is used to replace fossil fuels, it   2050.
          could push up climate-warming nitrous oxide pollution from   25.  Energy-intensive industries will have to slash their CO2 by 75%
                                                               to 90% by 2050, compared to 2010, in order to stick to 1.5C. A
       20.   How much carbon dioxide can be emitted before we pass   2C limit would require a 50% to 80% decline. This can be done
          the 1.5C threshold? The way “carbon budgets” are calculated   with new and existing technologies that are technically proven
          has changed since the IPCC’s last big assessment in 2014,   – but they have yet to be deployed on a large scale, and are
          adding some 300 gigatons to the estimate. But it’s still a slim   limited by costs and other constraints.
                                                            26.  Buildings and transport will also need to shift heavily towards
       21.    Estimates of the carbon budget vary depending on which   (newly green) electricity Buildings should use power for
          measure of warming you use. If you are going by the average   55% to 75% of their total energy by mid-century, while the
          temperature over land, it is 420Gt CO2 to give a 66%   transport sector should boost its low-emission sources to 35%
          chance of staying below 1.5C. If you factor in sea surface   to 65% of its energy supply, from less than 5% in 2020.
          temperatures, which are rising more slowly, it’s 570Gt. Either   27.  There will be tough choices around how to use land. A lot
          way, we are using up the budget at a rate of 42Gt a year.
                                                               of scenarios rely heavily on bioenergy and/or expansion of
       22.   There are also “substantial” uncertainties over how sensitive   forests, potentially conflicting with demand for pasture and
          the climate is to greenhouse gas emissions and the level of   arable land. Sustainable intensification of farming and “less
          historic emissions, which affect the size of the carbon budget.   resource-intensive diets” – code for eating less meat – can
          Additional carbon released when permafrost thaws, and   help ease the competing pressures.
          methane emitted from wetlands, could shrink the budget by   28.   Mitigating energy emissions for the 1.5C goal will require
          up to 100Gt over the century, and continue beyond it.
                                                               around $900 billion of investment per year between 2015 and
       23.  Geoengineering is given short shrift. So-called solar radiation   2050. That pushes the total investment needed for energy
          modification – pumping particles into the air to reflect sunlight   supply to $1.6-3.8 trillion, and for energy demand at $700bn
          – could be “theoretically effective” in reaching the 1.5C goal.   to $1trn over the 35 years. The investment needed is around
          But it is excluded from the model scenarios due to “large   12% higher than for 2C.

       An oil palm plantation in Indonesia. Food and energy crops are putting pressure on tropical forests (Pic: Nanang Sujana/CIFOR)

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