The potential for cuts in 2030 is 31 gigatons of CO2 equivalent – which isaround 52 per cent of global greenhouse gas emissions in 2023 – and 41gigatons in 2035.· Increased deployment of solar photovoltaic technologies and wind energy coulddeliver 27 per cent of this total emission reduction potential in 2030 and 38 percent in 2035.· Action on forests could deliver around 20 per cent of the potential in both years.• Other strong options include efficiency measures, electrification and fuelswitching in the buildings, transport and industry sectors.

The analysis presented in this ar-ticle offers some starting points for potentially fruitful dialogue.

What these communities have in common is that they collectively produce very useful—and typically high-quality—applications and information, but this without any financialcompensation or legal organization. In other words, these communities consist purely of volunteerscontributing on an informal basis to a common project. From the perspective of traditionaleconomics and organizational theory, this is paradoxical (Heylighen, 2007): why would anyoneprovide such valuable services to others without being either paid or ordered to do so? Severalauthors have investigated the motives that incite people to contribute to such communities (Ghosh,2005; Lerner & Tirole, 2002; Weber, 2004). These include curiosity, altruism, free expression, needfor belonging, desire for status and recognition, and the hope for future financial rewards for privateconsultancy after being publicly recognized for one’s expertise. More interesting for our purposethan these individual motivations, though, are the structures and processes that encourageindividuals to take part in such a collective enterprise, i.e. the underlying mobilization system.A first analysis (Heylighen, 2007) points at two fundamental mechanisms: feedback andstigmergy. By contributing a question, comment, answer, program, photo or any other input,participants hope to get a reaction from the other community members, because that would givethem an indication of whether they are on the right path, or need to make some correction. Suchfeedback provides valuable information that allows participants to get better in whatever they areinterested in. For example, a programmer who contributed a piece of code will benefit if a userpoints out a bug in that code, suggests a way to extend it, or simply confirms that the job was welldone.Stigmergy is a mechanism of spontaneous coordination between actions, where the result ofan individual’s work stimulates a next individual to continue that work (Parunak, 2006; Bolici,Howison, & Crowston, 2009; Heylighen, 2011a). For example, a paragraph contributed to aWikipedia article may incite a later reader of that paragraph to add a reference or further detail,which in turn may elicit further contributions from others.

effectively contribute and participate in upstream projects