This document provides a brief history of attacks on climate science, climate scientists, and the IPCC over the past 20 years by climate denial groups and individuals. It describes how in the early 1990s, fossil fuel industry groups like the Global Climate Coalition recruited spokespeople to publicly question the science and certainty of climate change. It traces key moments like attacks on the IPCC's first assessment report in 1990 and outlines how the denial campaign intensified with subsequent assessment reports in 1995, 2001, and 2007. The document also examines the tactics used in the campaign, including promoting misleading science, attacking individual scientists, and gaining political influence. It concludes that after 20 years, climate denial has taken deep root in some English-speaking countries.