Scientific consensus is the common opinion or agreement of most scientists in a certain field at a specific time.
Agreement is reached through scientists talking at conferences, publishing their work, others repeating their experiments to check results, discussions among experts, and reviewing each other's work.
Construction of scientific knowledge is first of all public, a collaborative effort among a community of peers working in a particular area. 'Collaborative' may seem a misnomer because individual scientists compete with each other in their debates about new knowledge claims. Yet this sense of collaboration is important: it checks individual scientists from being given authority for new knowledge claims prematurely.