The chapter details recent and future climate changes, primarily caused by anthropogenic emissions of greenhouse gases. This period of time is now commonly referred to as the Anthropocene. The chapter begins with a critical discussion of the hypothesis that anthropogenic activities have already begun to significantly impact the global climate since the mid-Holocene. The climate changes observed during the last century and their attribution to human activities are presented. The concept of anthropogenic emission scenarios and projections of future climate change are then described. The results of several future model simulations are shown, and the most robust aspects of future climate change projections and their potential impacts on natural systems and humanity are discussed. Finally, the possibility of predicting the very long-term future (beyond the current millennia) is discussed and possible scenarios are presented.

The chapter presents the diversity and mechanisms of climate variability during the late Quaternary interglacials. It begins by describing the nomenclature of interglacials and the difficulties associated with accurately defining their durations. The mechanisms of climate variability during interglacials are explored, with particular emphasis on the role of orbital forcing. The rest of the chapter outlines three of the most prominent late Quaternary interglacials – MIS 11, the Eemian interglacial and the Holocene. The cause for the long duration of MIS 11 is described. The patterns of climate change and the cause for the high sea level during the Eemian interglacial are linked to a strong orbital forcing. The climate variability during the Holocene, including the cold 8.2k event and the “green Sahara” phenomenon, is examined. The comparison between several interglacial periods with weak orbital forcing and their differences is explained using the concept of the critical insolation-CO2 relationship.

The chapter begins with a brief history of paleoclimate modeling. It first outlines the main modeling approaches and types of models used to study Quaternary climate dynamics. The hierarchy of numerical models is presented, ranging from simple (box, conceptual and 1-dimensional) models to comprehensive 3-D Earth system models. The role of models of intermediate complexity and of individual components of the Earth system in understanding past climate variability is explored. The use of different types of models to study past climate conditions and climate variability is illustrated through a number of practical examples. The methods of conducting time slice and transient experiments are compared, and their potential limitations are discussed. The chapter also explains the objective and methodology of the paleoclimate intercomparison projects and their main results.

The chapter describes Quaternary glacial cycles. It begins by outlining the main empirical evidence regarding the magnitude, typical periodicity and spatial pattern of Quaternary climate variability at orbital time scales, including changes in atmospheric composition and global ice volume. The chapter explores the current understanding of the mechanisms of Quaternary glacial cycles, starting with the classical Milankovitch theory, highlighting its strengths and shortcomings, and then provides an overview of modeling work carried out with different types of models aimed at testing the theory and reproducing the reconstructed climate variability associated with glacial cycles. The role of glacial-interglacial variations in atmospheric CO2 concentrations and the proposed mechanism of this variability are examined. The cause of the onset of Quaternary glacial cycles 2.7 million years ago and the transition from obliquity-dominated glacial cycles to the dominant 100,000-year periodicity one million years ago are discussed in relation to recent modeling results.

The chapter provides a brief summary of Earth's geological history, spanning from its origin to the Quaternary. It presents the main geological periods, key events and qualitative transitions in atmospheric composition, climate variability and the complex interaction between climate and life. It discusses the role of the Great Oxidation Event for climate and biosphere, the so-called “faint young sun paradox,” and the mechanisms behind the Neoproterozoic snowball Earth. The role of plate tectonics and the formation and collapse of supercontinents in climate history is described. The Paleocene and Eocene greenhouse climates and possible mechanisms of the Paleocene-Eocene Thermal Maximum are examined. The influence of a gradual Cenozoic cooling in the transition from a greenhouse to an icehouse world is explored alongside the leading hypothesis for the cause of Antarctic glaciation. Finally, the role of various factors in the transition to regular Quaternary glacial cycles is discussed.