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Abstract The Asian monsoon is a major component of the global climate system and can be divided into two subsystems, the Indian monsoon and the East Asian monsoon. Insights into monsoon behaviour and dynamics can be gained through studying past warm intervals in Earth's history. One such interval is the Pliocene epoch, specifically the mid-Piacenzian Warm Period (mPWP; 3.264–3.025 Ma). This time is characterised as a period of sustained warmth, with annual mean temperatures 2–3 °C higher than the pre-industrial era. Studies have examined the East Asian monsoon during the mPWP from both a geological data and climate modelling perspective. However, there has been little investigation into the behaviour of the Indian monsoon. Using a coupled atmosphere-ocean global climate model (HadCM3), the Indian summer monsoon response to orbital forcing during the mPWP is studied. Of the simulated interglacial events (Marine Isotope Stages KM5c, KM3, K1 and G17), MIS KM5c is the only one with a near-modern orbital forcing. This experiment is compared to a pre-industrial simulation to determine the nature of the mPWP Indian summer monsoon in the absence of a different pattern if insolation forcing. The monsoon at MIS KM5c, is simulated to be stronger than pre-industrial, with higher surface air temperatures and precipitation over land due to higher levels of CO 2. MIS G17, K1, and KM3 represent interglacial events of similar magnitude with different insolation forcing than MIS KM5c. The Indian summer monsoon is simulated to be significantly stronger for the interglacials K1 and KM3, compared to KM5c. This is due to stronger precession forcing causing an increase in summer surface air temperature and precipitation. When combined with Pliocene geological boundary conditions, these results highlight the significant effect of orbital forcing on the strength of the Indian summer monsoon. The sensitivity of the Indian monsoon to orbital forcing has important implications for any parallels drawn between Pliocene and future monsoon behaviour. Highlights • The Indian Summer Monsoon varied in response to orbital forcing in the Pliocene. • The monsoon is marginally stronger during an interglacial with a near modern orbit. • Interglacials with orbits very different from modern show an enhanced monsoon in the Pliocene. • The monsoon was significantly stronger during two interglacial events, MIS K1 and KM3. • Analogies drawn between the Pliocene and future Indian monsoon are too simplistic. [ABSTRACT FROM AUTHOR]

Abstract: The global submarine inventory of methane hydrate is thought to be considerable. The stability of marine hydrates is sensitive to changes in temperature and pressure and once destabilised, hydrates release methane into sediments and ocean and potentially into the atmosphere, creating a positive feedback with climate change. Here we present results from a multi-model study investigating how the methane hydrate inventory dynamically responds to different scenarios of future climate and sea level change. The results indicate that a warming-induced reduction is dominant even when assuming rather extreme rates of sea level rise (up to 20mmyr−1) under moderate warming scenarios (RCP 4.5). Over the next century modelled hydrate dissociation is focussed in the top of Arctic and Subarctic sediments beneath water depth. Predicted dissociation rates are particularly sensitive to the modelled vertical hydrate distribution within sediments. Under the worst case business-as-usual scenario (RCP 8.5), upper estimates of resulting global sea-floor methane fluxes could exceed estimates of natural global fluxes by 2100 , although subsequent oxidation in the water column could reduce peak atmospheric release rates to 0.75–1.4Tg CH4 yr−1. [Copyright &y& Elsevier]

• CO 2 increase leads to enhanced monsoonal precipitation over Asia. • Tibetan Plateau (TP) uplift linked to an intensified South Asian Monsoon. • Results show that the TP uplift is the main driver for climatic change in Asia. Today, the hydrological regime in East and South Asia is dominated by the monsoons, whilst central Asia is characterized as arid. Studies that have examined the onset of aridity and the intensification of the monsoons in Asia have generated significant debate, especially in respect to the timing of monsoon onset and how this relates to the potential causal mechanisms. The uplift of the Tibetan Plateau, the retreat of the Paratethys Sea, and the global cooling after the Eocene/Oligocene transition are all considered major drivers of Asian aridity and monsoonal intensification. However, little is known about each of these factor's contribution to the development of modern monsoon behaviour. Here, for the first time, we perform sensitivity simulations of a fully coupled ocean–atmosphere climate model (HadCM3) to investigate the effect of the Greenland and Antarctic ice-sheets formation, atmospheric carbon dioxide (CO 2) variability, and Tibetan Plateau uplift on East Central Asian aridity and monsoon driven precipitation. We focus on three individual regions, the South Asian Monsoon, the East Asian Monsoon and the Arid East Central Asia and we present the annual precipitation cycle and the moisture availability over each region. Our results show that of the parameters investigated the primary control on Asian hydroclimate is the topography of the Tibetan Plateau. Furthermore, our results highlight that the significance of each forcing depends on the component of the hydrological region and factors studied, a factor that proxy interpretation need to take into consideration. [ABSTRACT FROM AUTHOR]