Table SPM.1 Estimates of potential global greenhouse gas emission reductions in 2010 and in 2020

Table SPM.1 Estimates of potential global greenhouse gas emission reductions in 2010 and in 2020 (Sections 3.3 >3.8 and Chapter 3 Appendix)
Sector		Historic emissions in 1990	Historic C_eq annual growth rate in 1990-1995	Potential emission reductions in 2010	Potential emission reductions in 2020	Net direct costs per tonne of carbon avoided
		(MtCeq/yr)	(%)	(MtCeq/yr)	(MtCeq/yr)
Buildings ^a	CO₂ only	1,650	1.0	700-750	1,000-1,100	Most reductions are available at negative net direct costs.
Transport	CO₂ only	1,080	2.4	100-300	300-700	Most studies indicate net direct costs less than US$25/tC but two suggest net direct costs will exceed US$50/tC.
Industry	CO₂ only	2,300	0.4
-energy efficiency				300-500	700-900	More than half available at net negative direct costs.
-material efficiency				~200	~600	Costs are uncertain.
Industry	Non- CO₂ gases	170		~100	~100	N₂O emissions reduction costs are US$0-US$10/tC_eq.
Agriculture ^b	CO₂ only	210				Most reductions will cost between US$0-100/tC_eq with limited opportunities for negative net direct cost options.
	Non- CO₂ gases	1,250-2,800	n.a	150-300	350-750
Waste ^b	CH₄ only	240	1.0	~200	~200	About 75% of the savings as methane recovery from landfills at net negative direct cost; 25% at a cost of US$20/tC_eq.
Montreal Protocol	Non-CO₂ gases	0	n.a.	~100	n.a.	About half of reductions due to difference in study replacement applications baseline and SRES baseline values. Remaining half of the reductions available at net direct costs below US$200/tC_eq.
Energy supply and conversion ^c	CO₂ only	(1,620)	1.5	50-150	350-700	Limited net negative direct cost options exist; many options are available for less than US$100/tC_eq.
Total		6,900–8,400^d		1,900–2,600^e	3,600–5,050^e