This paper summarizes the importance of climate on tropical wetlands. Regional hydrology and carbon dynamics in many of these wetlands could shift with dramatic changes in these major carbon storages if the inter-tropical convergence zone (ITCZ) were to change in its annual patterns. The importance of seasonal pulsing hydrology on many tropical wetlands, which can be caused by watershed activities, orographic features, or monsoonal pulses from the ITCZ, is illustrated by both annual and 30-year patterns of hydrology in the Okavango Delta in southern Africa. Current studies on carbon biogeochemistry in Central America are attempting to determine the rates of carbon sequestration in tropical wetlands compared to temperate wetlands and the effects of hydrologic conditions on methane generation in these wetlands. Using the same field and lab techniques, we estimated that a humid tropical wetland in Costa Rica accumulated 255 g C m -2 year -1 in the past 42 years, 80% more than a similar temperate wetland in Ohio that accumulated 142 g C m -2 year -1 over the same period. Methane emissions averaged 1,080 mg-C m -2 day -1 in a seasonally pulsed wetland in western Costa Rica, a rate higher than methane emission rates measured over the same period from humid tropic wetlands in eastern Costa Rica (120-278 mg-C m -2 day -1 ). Tropical wetlands are often tuned to seasonal pulses of water caused by the seasonal movement of the ITCZ and are the most likely to be have higher fire frequency and changed methane emissions and carbon oxidation if the ITCZ were to change even slightly.

In the period 2015-2017, the Western Cape region has suffered from three consecutive years of below average rainfall-leading to a prolonged drought and acute water shortages, most prominently in the city of Cape Town. After testing that the precipitation deficit is the primary driver behind the reduced surface water availability, we undertake a multi-method attribution analysis for the meteorological drought, defined in terms of a deficit in the 3 years running mean precipitation averaged over the Western Cape area. The exact estimate of the return time of the event is sensitive to the number of stations whose data is incorporated in the analysis but the rarity of the event is unquestionable, with a return time of more than a hundred years. Synthesising the results from five different large model ensembles as well as observed data gives a significant increase by a factor of three (95% confidence interval 1.5-6) of such a drought to occur because of anthropogenic climate change. All the model results further suggest that this trend will continue with future global warming. These results are in line with physical understanding of the effect of climate change at these latitudes and highlights that measures to improve Cape Town's resilience to future droughts are an adaptation priority.

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Characterising inundation conditions for flood-pulsed wetlands is a critical first step towards assessment of flood risk as well as towards understanding hydrological dynamics that underlay their ecology and functioning. In this paper, we develop a series of inundation maps for the Okavango Delta, Botswana, based on the thresholding of the SWIR band (b7) MODIS MCD43A4 product. We show that in the Okavango Delta, SWIR is superior to other spectral bands or derived indices, and illustrate an innovative way of defining the spectral threshold used to separate inundated from dry land. The threshold is determined dynamically for each scene based on reflectances of training areas capturing end-members of the inundation spectrum. The method provides a very good accuracy and is suitable for automated processing.

a b s t r a c tRecent trends in abrupt weather changes continue to pose a challenge to agricultural production most especially in sub-Saharan Africa. The paper specifically addresses the questions on how local farmers read and predict the weather; and how they can collaborate with weather scientists in devising adaptation strategies for climate variability (CV) in the Okavango Delta of Botswana. Recent trends in agriculture-related weather variables available from country's climate services, as well as in freely available satellite rainfall products were analysed. The utility of a seasonal hydrological forecasting system for the study area in the context of supporting farmer's information needs were assessed. Through a multi-stage sampling procedure, a total of 592 households heads in 8 rural communities in the Okavango Delta were selected and interviewed using open and close-ended interview schedules. Also, 19 scientists were purposively selected and interviewed using questionnaires. Key informant interviews, focus group and knowledge validation workshops were used to generate qualitative information from both farmers and scientists. Descriptive and inferential statistics were used in summarising the data. Analysis of satellite rainfall products indicated that there was a consistent increase in total annual rainfall throughout the region in the last 10 years, accompanied by an increase in number of rain days, and reduction of duration of dry spells. However, there is a progressive increase in the region's temperatures leading to increase in potential evaporation. Findings from social surveys show that farmers' age, education level, number of years engaged in farming, sources of weather information, knowledge of weather forecasting and decision on farming practices either had a significant relationship or correlation with their perceptions about the nature of both local [ethno-meteorological] and scientific weather knowledge. Nonetheless, there was a significant difference in the mean scores of farmers in relation to their perceptions and those of the climate scientists about the nature of both local and Western knowledge. As farmers are adept at judging seasonal patterns through long-standing ethno-meteorology, one major CV adaptation measure is their ability to anticipate changes in future weather conditions, which enables them to adjust their farming calendars and make decisions on crop type selection in any given season.